Polybenzimidazole copolymers and novel proton exchange membranes, methods of making and use thereof

Abstract

The application relates to the technical field of polybenzimidazole, and discloses a polybenzimidazole copolymer, a novel proton exchange membrane and a preparation method and application thereof; the proton exchange membrane comprises a matrix and a proton active component; the matrix is a polybenzimidazole homopolymer; the proton active component is a polybenzimidazole copolymer; and the polybenzimidazole copolymer comprises a first structural unit and a second structural unit. The proton exchange membrane of the application adopts a polybenzimidazole homopolymer as the matrix, and simultaneously adopts a polybenzimidazole copolymer containing a nitrogen-containing heterocyclic structural unit as the proton active component, so that the proton exchange membrane of the application has higher acid loading capacity (especially phosphoric acid loading capacity) and proton conductivity, and simultaneously has good mechanical properties and dimensional stability.

Description

Technical Field

[0001] This invention relates to the field of polybenzimidazole technology, specifically to a polybenzimidazole copolymer and a novel proton exchange membrane, as well as their preparation methods and applications. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) offer advantages such as low pollution, low noise, and high efficiency, making them a promising type of hydrogen fuel cell. Currently, low-temperature PEMFCs, operating below 100°C, are widely used in the market. These fuel cells suffer from complex hydrothermal management, low tolerance to impurities in hydrogen, and susceptibility to catalyst poisoning. High-temperature PEMFCs (HT-PEMFCs), operating above 120°C, offer simpler hydrothermal management, higher tolerance to impurities, and can reduce the use of precious metal catalysts, making them a research hotspot in recent years.

[0003] High-temperature resistant proton exchange membranes are a core component of HT-PEMFCs. Polybenzimidazole (PBI) is an aromatic heterocyclic polymer containing repeating benzimidazole structural units in its main chain. Due to its excellent high-temperature resistance, chemical stability, and mechanical properties, it is considered an ideal material for preparing high-temperature resistant proton exchange membranes. Pure PBI membranes have extremely low proton conductivity, but after loading with phosphoric acid, the proton conductivity of PBI membranes increases significantly. Phosphoric acid-loaded proton exchange membranes made using PBI have been applied in the research field of HT-PEMFCs.

[0004] However, the plasticizing effect caused by phosphoric acid loading deteriorates the mechanical properties of PBI films. PBI films with high phosphoric acid loading typically exhibit lower mechanical properties and poor dimensional stability, adversely affecting subsequent battery assembly and operation. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a polybenzimidazole copolymer and a novel proton exchange membrane, as well as their preparation method and application. The novel proton exchange membrane of this invention not only has a high acid loading and proton conductivity, but also good mechanical properties and dimensional stability.

[0006] The inventors of this invention unexpectedly discovered that proton exchange membranes prepared using polybenzimidazole homopolymers and the polybenzimidazole copolymers containing nitrogen-containing heterocyclic structural units of this invention not only have high acid loading and proton conductivity, but also good mechanical properties and dimensional stability.

[0007] To achieve the above objectives, a first aspect of the present invention provides a proton exchange membrane, the proton exchange membrane comprising a matrix and a proton-active component, wherein the matrix is ​​a polybenzimidazole homopolymer, and the proton-active component is a polybenzimidazole copolymer, the polybenzimidazole copolymer comprising a first structural unit and a second structural unit, wherein the first structural unit has the structure shown in formula (2), and the second structural unit has the structure shown in formula (3).

[0008]

[0009] R3 and R5 are each independently selected from one of the following structural units:

[0010]

[0011] Wherein, X is selected from one of the following structural units:

[0012]

[0013] R4 is selected from one of the following structural units:

[0014]

[0015] Where n = 2 - 10;

[0016] R6 is a nitrogen-containing heterocyclic structural unit.

[0017] A second aspect of the present invention provides a method for preparing a proton exchange membrane, the method comprising preparing a membrane from a solution containing a matrix and a proton-active component, wherein the matrix is ​​a polybenzimidazole homopolymer, the proton-active component is a polybenzimidazole copolymer, and the polybenzimidazole copolymer is as described in the first aspect.

[0018] A third aspect of the present invention provides a proton exchange membrane prepared by the method described above.

[0019] A fourth aspect of the present invention provides an acid-supported proton exchange membrane, which includes the proton exchange membrane described above and an acid supported on the proton exchange membrane.

[0020] The fifth aspect of the present invention provides the application of the proton exchange membrane described above and / or the acid-supported proton exchange membrane described above in improving the conductivity of the proton exchange membrane.

[0021] The sixth aspect of the present invention provides a polybenzimidazole copolymer comprising a first structural unit and a second structural unit as described in the first aspect.

[0022] Through the above technical solution, the present invention achieves the following beneficial effects:

[0023] (1) The proton exchange membrane of the present invention uses polybenzimidazole homopolymer as the matrix and polybenzimidazole copolymer containing nitrogen-containing heterocyclic structural units as the proton active component, thereby giving the proton exchange membrane of the present invention a high acid loading (especially phosphoric acid loading) and proton conductivity, as well as good mechanical properties and dimensional stability.

[0024] (2) The method for preparing proton exchange membranes in this invention is simple, and the mixing process of the matrix and proton active components is convenient and simple, making it suitable for large-scale industrial production; and the prepared proton exchange membrane can have both excellent mechanical properties and proton conductivity.

[0025] (3) Preferably, when the molar ratio of the first structural unit and the second structural unit of the polybenzimidazole copolymer containing nitrogen heterocyclic structural units provided by the present invention is within a specific range, the proton exchange membrane prepared not only has a high phosphate loading, but also a high proton conductivity. Attached Figure Description

[0026] Figure 1 This is the 1H NMR spectrum of mbpy-PBI-8-2;

[0027] Figure 2 This is the 1H NMR spectrum of mbpy-PBI-9-1;

[0028] Figure 3 This is the 1H NMR spectrum of mbpy-PBI-5-5. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] The first aspect of the present invention provides a proton exchange membrane, the proton exchange membrane comprising a matrix and a proton-active component, wherein the matrix is ​​a polybenzimidazole homopolymer, and the proton-active component is a polybenzimidazole copolymer, the polybenzimidazole copolymer comprising a first structural unit and a second structural unit, wherein the first structural unit has the structure shown in formula (2), and the second structural unit has the structure shown in formula (3).

[0031]

[0032] R3 and R5 are each independently selected from one of the following structural units:

[0033]

[0034] Wherein, X is selected from one of the following structural units:

[0035]

[0036] R4 is selected from one of the following structural units:

[0037]

[0038] Where n = 2 - 10;

[0039] R6 is a nitrogen-containing heterocyclic structural unit.

[0040] According to the present invention, preferably, R6 is selected from one of pyridinyl subunit, bipyridinyl subunit, pyrrole subunit, imidazole subunit, quinoline subunit, thiophene subunit, pyrazine subunit, and piperidine subunit; more preferably, R6 is selected from one of the following structural units:

[0041]

[0042] According to a particularly preferred embodiment of the present invention, R6 is selected from... For example,

[0043] One of them; particularly preferably, R6 is selected from

[0044] According to the present invention, preferably, the molar ratio of the structure shown in formula (2) and the structure shown in formula (3) in the polybenzimidazole copolymer is 0.05-20:1, more preferably 1-10:1. The content of structural units in the present invention is calculated based on the amount of feed. In the present invention, the molar ratio of the structure shown in formula (2) and the structure shown in formula (3) in the polybenzimidazole copolymer can be 0.05:1, 0.1:1, 0.5:1, 1:1, 1.2:1, 1.5:1, 2:1, 3:1, 3.5:1, 3.8:1, 4:1, 4.1:1, 4.5:1, 5:1, 6:1, 7:1, 8:1, 8.5:1, 8.9:1, 9:1, 9.1:1, 9.5:1, 10:1, 15:1, 20:1, and any two of the above ranges.

[0045] According to a preferred embodiment of the present invention, the first structural unit has the structure shown in formula (2').

[0046]

[0047] According to a preferred embodiment of the present invention, the first structural unit has the structure shown in formula (3').

[0048]

[0049] According to the present invention, preferably, the polybenzimidazole homopolymer has the structure shown in formula (1).

[0050]

[0051] R1 is selected from one of the following structural units:

[0052]

[0053] Wherein, X is selected from one of the following structural units:

[0054]

[0055] R2 is selected from one of the following structural units:

[0056]

[0057] Where n = 2 - 10.

[0058] According to a preferred embodiment of the present invention, the polybenzimidazole homopolymer has the structure shown in formula (1').

[0059]

[0060] According to the present invention, in order to further improve the acid loading and proton conductivity of the proton exchange membrane while also possessing good mechanical properties, preferably, the viscosity-average molecular weight of the polybenzimidazole homopolymer is 10,000-500,000 g / mol, more preferably 60,000-200,000 g / mol, and even more preferably 80,000-170,000 g / mol (e.g., 80,000 g / mol, 85,000 g / mol, 90,000 g / mol, 95,000 g / mol, 100,000 g / mol). 105000 g / mol, 110000 g / mol, 115000 g / mol, 120000 g / mol, 125000 g / mol, 130000 g / mol, 135000 g / mol, 140000 g / mol, 145000 g / mol, 150000 g / mol, 155000 g / mol, 160000 g / mol, 165000 g / mol, 170000 g / mol, and any two of the above ranges).

[0061] According to the present invention, in order to further improve the acid loading and proton conductivity of the proton exchange membrane while also possessing good mechanical properties, preferably, the viscosity-average molecular weight of the polybenzimidazole copolymer is 1000-100000 g / mol, more preferably 5000-60000 g / mol, and even more preferably 30000-60000 g / mol (e.g., 30000 g / mol, 35000 g / mol, 40000 g / mol, 45000 g / mol, 50000 g / mol, 55000 g / mol, 60000 g / mol, and any two of the above ranges).

[0062] According to the present invention, in order to further improve the proton conductivity of the proton exchange membrane, preferably, based on the total weight of the matrix and the proton-active component, the content of the proton-active component is 5-50% by weight (e.g., 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, and any two of the above), more preferably 10-40% by weight, and even more preferably 10-40% by weight.

[0063] According to a particularly preferred embodiment of the present invention, the structural formula of the polybenzimidazole homopolymer in the proton exchange membrane is shown in formula (1-1), the structural formula of the first structural unit in the polybenzimidazole copolymer is shown in formula (2-1), and the structural formula of the second structural unit in the polybenzimidazole copolymer is shown in formula (3-1).

[0064]

[0065] According to a particularly preferred embodiment of the present invention, the polybenzimidazole homopolymer in the proton exchange membrane has the structural formula shown in formula (1-1), and the viscosity-average molecular weight of the polybenzimidazole homopolymer is 80,000-115,000 g / mol; the structural formula of the first structural unit in the polybenzimidazole copolymer is shown in formula (2-1), and the structural formula of the second structural unit in the polybenzimidazole copolymer is shown in formula (3-1), and the viscosity-average molecular weight of the polybenzimidazole copolymer is 40,000-50,000 g / mol. More preferably, the molar ratio of the structure shown in formula (2-1) to the structure shown in formula (3-1) in the polybenzimidazole copolymer is 4-9:1.

[0066] According to a particularly preferred embodiment of the present invention, the polybenzimidazole homopolymer in the proton exchange membrane has the structural formula shown in formula (1-1), and the viscosity-average molecular weight of the polybenzimidazole homopolymer is 80,000-95,000 g / mol; the structural formula of the first structural unit in the polybenzimidazole copolymer is shown in formula (2-1), and the structural formula of the second structural unit in the polybenzimidazole copolymer is shown in formula (3-1), and the viscosity-average molecular weight of the polybenzimidazole copolymer is 40,000-50,000 g / mol. More preferably, the molar ratio of the structure shown in formula (2-1) to the structure shown in formula (3-1) in the polybenzimidazole copolymer is 4-9:1.

[0067] According to a particularly preferred embodiment of the present invention, the polybenzimidazole homopolymer in the proton exchange membrane has the structural formula shown in formula (1-1), and the viscosity-average molecular weight of the polybenzimidazole homopolymer is 80,000-85,000 g / mol; the first structural unit in the polybenzimidazole copolymer has the structural formula shown in formula (2-1), and the second structural unit in the polybenzimidazole copolymer has the structural formula shown in formula (3-1), and the viscosity-average molecular weight of the polybenzimidazole copolymer is 40,000-45,000 g / mol. More preferably, the molar ratio of the structure shown in formula (2-1) to the structure shown in formula (3-1) in the polybenzimidazole copolymer is 8-9:1. The proton exchange membrane prepared using this particularly preferred embodiment can not only further improve the proton conductivity, but also further improve the mechanical properties and reduce the amount of proton active component used.

[0068] A second aspect of the present invention provides a method for preparing a proton exchange membrane, the method comprising preparing a membrane from a solution containing a matrix and a proton-active component, wherein the matrix is ​​a polybenzimidazole homopolymer, the proton-active component is a polybenzimidazole copolymer, and the polybenzimidazole copolymer is as described in the first aspect.

[0069] According to the present invention, the type of solvent is not particularly limited, as long as it can dissolve the matrix and the proton-active component to form a homogeneous solution. Preferably, the solvent in the solution containing the matrix and the proton-active component is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, formic acid, and phosphoric acid.

[0070] According to the present invention, the amount of solvent in the solution can be selected within a wide range, as long as the dissolution of the matrix and proton-active components is guaranteed. Preferably, the solvent content in the solution containing the matrix and proton-active components is 90-99.9% by weight, more preferably 95-99.5% by weight.

[0071] The film formation method of the present invention can be any film formation method commonly used in the art, such as solution casting, solution casting, solution blow molding, and solution coating. According to a specific embodiment of the present invention, the method for preparing the proton exchange membrane includes: mixing a matrix and a proton-active component with a solvent, then heating the mixture at 40-120°C to form a solution, pouring the solution onto a flat glass plate, and then drying it at 30-150°C to obtain the membrane.

[0072] According to the present invention, preferably, the polybenzimidazole homopolymer and the polybenzimidazole copolymer are each independently as described in the first aspect, and will not be repeated here.

[0073] A third aspect of the present invention provides a proton exchange membrane prepared by the method described above.

[0074] A fourth aspect of the present invention provides an acid-supported proton exchange membrane, which includes the proton exchange membrane described above and an acid supported on the proton exchange membrane.

[0075] According to the present invention, preferably, the acid is selected from at least one of phosphoric acid, phosphotungstic acid, tungstic acid, nitric acid, sulfuric acid, perchloric acid, and hydrochloric acid.

[0076] According to the present invention, preferably, the acid loading in the acid-loaded proton exchange membrane is 200-700 wt%, more preferably 300-600 wt%.

[0077] According to the present invention, the preparation method of the acid-loaded proton exchange membrane can be the acid loading method commonly used in the art. The present invention also provides a method for preparing an acid-loaded proton exchange membrane, which includes immersing the proton exchange membrane in acid at 20-180°C for 1-72 hours. At the end of the immersion, the residual acid on the surface is wiped dry with filter paper to obtain the acid-loaded proton exchange membrane.

[0078] The fifth aspect of the present invention provides the application of the proton exchange membrane described above and / or the acid-supported proton exchange membrane described above in improving the conductivity of the proton exchange membrane.

[0079] The sixth aspect of the present invention provides a polybenzimidazole copolymer comprising a first structural unit and a second structural unit as described in the first aspect.

[0080] According to the present invention, preferably, the first structural unit has the structural formula shown in formula (2-1), and the second structural unit has the structural formula shown in formula (3-1).

[0081]

[0082] According to the present invention, preferably, the molar ratio of the structure shown in formula (2-1) to the structure shown in formula (3-1) in the polybenzimidazole copolymer is 0.05-20:1, more preferably 1-10:1.

[0083] The present invention will be described in detail below through embodiments. In the following embodiments,

[0084] (1) The intrinsic viscosity of polybenzimidazole (PBI) was obtained by the Ubbelohde viscometer method: PBI powder was dissolved in concentrated sulfuric acid (98 wt%) to prepare a sulfuric acid solution with a concentration of 0.6 g / dL. The sulfuric acid solution was added to an Ubbelohde viscometer with a capillary inner diameter of 1.0-1.1 mm and stabilized in a constant temperature water bath at 25℃ for 30 min. The outflow time of the solution was recorded as t1, the outflow time of the concentrated sulfuric acid was recorded as t0, and the concentration of the polymer solution was recorded as C. The intrinsic viscosity of PBI was calculated according to Formula 1 and Formula 2.

[0085] Increased specific viscosity

[0086] Intrinsic viscosity

[0087] The viscosity-average molecular weight M of the polymer is obtained from Formula 3, where the constant is taken as K = 1.94 × 10⁻⁶. -4 , α=0.791.

[0088] [η]=KM α Formula 3

[0089] (2) Volume swelling rate and phosphoric acid loading: Record the mass of the membrane before and after soaking in phosphoric acid, denoted as W1 and W2 respectively, and the volume as S1 and S2. The volume swelling rate of the PBI membrane is calculated according to Formula 4. The phosphoric acid loading of the PBI membrane is calculated according to Formula 5.

[0090]

[0091] (3) Proton conductivity: The polybenzimidazole proton exchange membrane loaded with phosphoric acid was cut into strips and placed in a two-electrode test system to test its bulk impedance (Rb), where l is the length of the strip between the two electrodes and A is the cross-sectional area of ​​the strip; the proton conductivity (σ) was calculated according to formula 6.

[0092]

[0093] (4) Mechanical properties: The mechanical properties of the film strip loaded with phosphoric acid were tested at room temperature (25±2)℃ and humidity (50±10)% using an Instron 5965 universal tensile testing instrument with a tensile rate of 1mm / min.

[0094] All raw materials are commercially available.

[0095] Preparation Example 1

[0096] This preparation example illustrates the preparation method of OPBI homopolymer.

[0097] 60 g of polyphosphoric acid was weighed and, under nitrogen protection, 10 mmol of 3,3'-diaminobenzidine and 10 mmol of 4,4'-dicarboxylic acid diphenyl ether were added. The mixture was heated to 200 °C with mechanical stirring and reacted for 5 h. The reaction solution was then washed in a saturated sodium carbonate aqueous solution until neutral, filtered, and the product was dried in a vacuum oven at 80 °C. The viscosity-average molecular weight of the product was 8.29 × 10⁻⁶. 4 g / mol, the product was labeled as OPBI-8W.

[0098] Preparation Example 2

[0099] This preparation example illustrates the preparation method of OPBI homopolymer.

[0100] The preparation method was carried out as in Example 1, except that the reaction time was 6 hours. The viscosity-average molecular weight of the product was 9.24 × 10⁻⁶. 4 g / mol, the product was labeled as OPBI-9W.

[0101] Preparation Example 3

[0102] This preparation example illustrates the preparation method of OPBI homopolymer.

[0103] The preparation method was carried out as in Example 1, except that the reaction time was 7 hours. The viscosity-average molecular weight of the product was 11.4 × 10⁻⁶. 4 g / mol, the product was labeled as OPBI-11W.

[0104] Preparation Example 4

[0105] This preparation example illustrates the preparation method of bpy-PBI homopolymer.

[0106] The preparation method was carried out according to Example 1, except that the reactants were 3,3'-diaminobenzidine (10 mmol) and 2,2'-bipyridine-5,5'-dicarboxylic acid (10 mmol), and the reaction time was 8 h. The product was labeled as bpy-PBI. The viscosity-average molecular weight of bpy-PBI was 3.9 × 10⁻⁶. 4 g / mol.

[0107] Preparation Example 5

[0108] This preparation example illustrates the preparation method of the mbpy-PBI copolymer.

[0109] The preparation method was carried out according to Example 1, except that the reactants were 3,3'-diaminobenzidine (10 mmol), isophthalic acid (5 mmol), and 2,2'-bipyridine-5,5'-dicarboxylic acid (5 mmol), and the reaction time was 8 h. The product was labeled mbpy-PBI-5-5. The viscosity-average molecular weight of mbpy-PBI-5-5 was 3.52 × 10⁻⁶. 4 g / mol. The 1H NMR spectrum of mbpy-PBI-5-5 is shown below. Figure 3 .

[0110] Preparation Example 6

[0111] This preparation example illustrates the preparation method of the mbpy-PBI copolymer.

[0112] The preparation method was carried out according to Example 1, except that the reactants were 3,3'-diaminobenzidine (10 mmol), isophthalic acid (8 mmol), and 2,2'-bipyridine-5,5'-dicarboxylic acid (2 mmol), and the reaction time was 8 h. The product was labeled as mbpy-PBI-8-2. The viscosity-average molecular weight of mbpy-PBI-8-2 was 4.68 × 10⁻⁶. 4 g / mol. The 1H NMR spectrum of mbpy-PBI-8-2 is shown below. Figure 1 .

[0113] Preparation Example 7

[0114] This preparation example illustrates the preparation method of the mbpy-PBI copolymer.

[0115] The preparation method was carried out according to Example 1, except that the reactants were 3,3'-diaminobenzidine (10 mmol), isophthalic acid (9 mmol), and 2,2'-bipyridine-5,5'-dicarboxylic acid (1 mmol), and the reaction time was 8 h. The product was labeled as mbpy-PBI-9-1. The viscosity-average molecular weight of mbpy-PBI-9-1 was 4.43 × 10⁻⁶. 4 g / mol. The 1H NMR spectrum of mbpy-PBI-9-1 is shown below. Figure 2 .

[0116] Example 1

[0117] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0118] (1) Weigh 0.4g OPBI-11W and 0.1g mbpy-PBI-8-2, add them to 16g N,N-dimethylacetamide, heat and stir at 80℃ for 8h to form a uniform solution, pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0119] (2) The membrane was immersed in an 85% phosphoric acid aqueous solution and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0120] Example 2

[0121] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0122] The procedure was carried out according to Example 1, except that the amounts of OPBI-11W and mbpy-PBI-8-2 added were 0.3g and 0.2g, respectively.

[0123] Example 3

[0124] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0125] (1) Weigh 0.4g OPBI-9W and 0.1g mbpy-PBI-8-2, add them to 20g N,N-dimethylacetamide, heat and stir at 80℃ for 8h to form a uniform solution, pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0126] (2) The membrane was immersed in 85% phosphoric acid and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0127] Example 4

[0128] The procedure was carried out according to Example 3, except that the amounts of OPBI-9W and mbpy-PBI-8-2 added were 0.3g and 0.2g, respectively.

[0129] Example 5

[0130] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0131] (1) Weigh 0.45g OPBI-8W and 0.05g mbpy-PBI-8-2, add them to 18g N,N-dimethylacetamide, heat and stir at 80℃ for 8h to form a uniform solution, pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0132] (2) The membrane was immersed in an 85% phosphoric acid aqueous solution and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0133] Example 6

[0134] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0135] The procedure was carried out according to Example 5, except that the amounts of OPBI-8W and mbpy-PBI-8-2 added were 0.4g and 0.1g, respectively.

[0136] Example 7

[0137] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0138] (1) Weigh 0.3g OPBI-11W and 0.2g mbpy-PBI-5-5, add them to 20g N,N-dimethylacetamide, heat and stir at 80℃ for 8h to form a uniform solution, pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0139] (2) The membrane was immersed in 85% phosphoric acid and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0140] Example 8

[0141] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0142] (1) Weigh 0.45g OPBI-8W and 0.05g mbpy-PBI-9-1, add them to 20g N,N-dimethylacetamide, heat and stir at 80℃ for 8h to form a uniform solution, pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0143] (2) The membrane was immersed in 85% phosphoric acid and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0144] Example 9

[0145] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0146] (1) Weigh 0.5g mbpy-PBI-9-1 and add it to 20g N,N-dimethylacetamide. Heat and stir at 80℃ for 8h to form a uniform solution. Pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0147] (2) The membrane was immersed in an 85% phosphoric acid aqueous solution and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0148] Example 10

[0149] This embodiment illustrates the preparation method of a phosphate-supported proton exchange membrane.

[0150] (1) Weigh 0.5g mbpy-PBI-8-2 and add it to 20g N,N-dimethylacetamide. Heat and stir at 80℃ for 8h to form a uniform solution. Pour the solution onto a flat glass plate and dry at 70℃ to form a film.

[0151] (2) The membrane was immersed in 85% phosphoric acid and loaded at 60°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0152] Comparative Example 1

[0153] This comparative example illustrates the preparation method of phosphate-supported proton exchange membranes.

[0154] (1) Weigh 0.5g of OPBI-8W and add it to 16g of N,N-dimethylacetamide. Heat and stir at 80°C for 8 hours to form a uniform solution. Pour the solution onto a flat glass plate and dry it at 70°C to form a film.

[0155] (2) The membrane was immersed in an 85% phosphoric acid aqueous solution and loaded at 80°C for 24 hours. After that, it was taken out and the residual phosphoric acid on the surface was wiped off with filter paper to obtain a phosphoric acid loaded proton exchange membrane.

[0156] Comparative Examples 2-5

[0157] This comparative example illustrates the preparation method of phosphate-supported proton exchange membranes.

[0158] The procedure was carried out in accordance with Comparative Example 1, except that OPBI-8W was replaced in sequence with OPBI-9W, OPBI-11W, bpy-PBI, and mbpy-PBI-5-5 prepared in Preparation Examples 2-5.

[0159] Among them, bpy-PBI is insoluble in solvents, so bpy-PBI membranes cannot be obtained.

[0160] In particular, when mbpy-PBI-5-5 is loaded with phosphoric acid, the PBI membrane dissolves in the phosphoric acid, making it impossible to perform proton conductivity tests.

[0161] Comparative Example 6

[0162] This comparative example illustrates the preparation method of phosphate-supported proton exchange membranes.

[0163] Weigh 0.4g of OPBI-11W and 0.1g of bpy-PBI, add them to 16g of N,N-dimethylacetamide, and heat and stir at 80℃ for 8h. The sample has poor solubility in the solvent and is gel-like, so a membrane cannot be obtained.

[0164] Test case

[0165] The phosphoric acid loading, volume swelling ratio, proton conductivity, and tensile fracture strength of the proton exchange membranes in the above embodiments and comparative examples were tested. The test results are shown in Table 1.

[0166] Table 1

[0167]

[0168] As can be seen from Table 1, compared with Comparative Examples 1-6, the proton exchange 1240095 prepared in the embodiments of the present invention...

[0169] I94661BHY

[0170] The membrane not only possesses high acid loading and proton conductivity, but also exhibits excellent mechanical properties and dimensional stability. Preferably, the proton exchange membranes prepared in Examples 1-2, 4, and 8 of this invention achieve even better results, ensuring a tensile breaking strength of over 4 MPa after loading with phosphoric acid, while maintaining a proton conductivity of over 40 mS / cm.

[0171] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A proton exchange membrane, characterized in that, The proton exchange membrane comprises a matrix and a proton-active component. The matrix is ​​a polybenzimidazole homopolymer, and the proton-active component is a polybenzimidazole copolymer. The polybenzimidazole copolymer comprises a first structural unit and a second structural unit, wherein the first structural unit has the structure shown in formula (2), and the second structural unit has the structure shown in formula (3). R3 and R5 are each independently selected from one of the following structural units: Wherein, X is selected from one of the following structural units: -YOU-, R4 is selected from one of the following structural units: Where n = 2 - 10; R6 is a nitrogen-containing heterocyclic structural unit.

2. The proton exchange membrane according to claim 1, wherein, R6 is selected from one of the following structural units: pyridinium subunit, bipyridinium subunit, pyrrole subunit, imidazole subunit, quinoline subunit, thiophene subunit, pyrazine subunit, and piperidine subunit; more preferably, R6 is selected from one of the following structural units:

3. The proton exchange membrane according to claim 1, wherein, The molar ratio of the structure shown in formula (2) to the structure shown in formula (3) in the polybenzimidazole copolymer is 0.05-20:1, preferably 1-10:

1.

4. The proton exchange membrane according to claim 1, wherein, The polybenzimidazole homopolymer has the structure shown in formula (1). R1 is selected from one of the following structural units: Wherein, X is selected from one of the following structural units: -YOU-, R2 is selected from one of the following structural units: Where n = 2 - 10.

5. The proton exchange membrane according to any one of claims 1-4, wherein, The viscosity-average molecular weight of the polybenzimidazole homopolymer is 10,000-500,000 g / mol, more preferably 60,000-200,000 g / mol; And / or, the viscosity-average molecular weight of the polybenzimidazole copolymer is 1,000-100,000 g / mol, more preferably 5,000-60,000 g / mol; And / or, based on the total weight of the matrix and the proton-active component, the content of the proton-active component is 5-50% by weight.

6. A method for preparing a proton exchange membrane, characterized in that, The method includes preparing a film from a solution containing a matrix and a proton-active component, wherein the matrix is ​​a polybenzimidazole homopolymer, the proton-active component is a polybenzimidazole copolymer, and the polybenzimidazole copolymer is as described in any one of claims 1-5.

7. The method according to claim 6, wherein, The solvent in the solution containing the matrix and proton-active components is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, formic acid, and phosphoric acid. Preferably, the solvent content in the solution containing the matrix and proton-active components is 90-99.9% by weight, and more preferably 95-99.5% by weight; And / or, the polybenzimidazole homopolymer is as described in any one of claims 1-5.

8. The proton exchange membrane prepared by the method of claim 6 or 7.

9. An acid-supported proton exchange membrane, characterized in that, The acid-supported proton exchange membrane includes the proton exchange membrane according to any one of claims 1-5 and 8 and the acid supported on the proton exchange membrane.

10. The acid-supported proton exchange membrane according to claim 9, wherein, The acid is selected from at least one of phosphoric acid, phosphotungstic acid, tungstic acid, nitric acid, sulfuric acid, perchloric acid, and hydrochloric acid; And / or, the acid loading in the acid-loaded proton exchange membrane is 200-700% by weight, preferably 300-600% by weight.

11. The use of the proton exchange membrane according to any one of claims 1-5 and 8 and / or the acid-supported proton exchange membrane according to claim 9 or 10 in improving the conductivity of proton exchange membranes.

12. A polybenzimidazole copolymer, characterized in that, The polybenzimidazole copolymer includes a first structural unit and a second structural unit as described in any one of claims 1-5.

13. The polybenzimidazole copolymer according to claim 12, wherein, The structural formula of the first structural unit is shown in equation (2-1), and the structural formula of the second structural unit is shown in equation (3-1). Preferably, the molar ratio of the structure shown in formula (2-1) to the structure shown in formula (3-1) in the polybenzimidazole copolymer is 0.05-20:1, and more preferably 1-10:1.

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