Steric hindrance branched polybenzimidazole basic ion solvated membrane as well as preparation method and application of steric hindrance branched polybenzimidazole basic ion solvated membrane

Abstract

The invention discloses a steric hindrance branched polybenzimidazole basic ion solvent film as well as a preparation method and application thereof, and mainly relates to the technical field of energy conversion. According to the steric hindrance branched polybenzimidazole disclosed by the invention, a steric hindrance dicarboxylic acid monomer, a branched aryl tricarboxylic acid or tetracarboxylic acid monomer and biphenyl tetramine are subjected to polycondensation in a polymerization reaction process, and other alkaline dicarboxylic acid monomers can be supplemented in the polycondensation process, so that a series of novel steric hindrance branched polybenzimidazole is prepared. The prepared polybenzimidazole polymer is subjected to film forming treatment and then is doped with alkali, and the steric hindrance branched polybenzimidazole alkaline ion solvated film is obtained. The ionic solvent membrane constructed based on the polymer can also be widely applied to new energy devices such as alkaline zinc-air cells, ammonia fuel cells and carbon dioxide electroreduction, and has a good application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of alkaline water electrolysis, and in particular to a sterically hindered branched polybenzimidazole alkaline ion solvation membrane and a preparation method and application thereof. Background Art

[0002] The extensive use of fossil fuels has led to the depletion of fossil fuel resources and triggered serious energy crises and environmental problems. As the concept of sustainable development has gained popularity, the development of green, renewable, and low-carbon energy has gradually become a consensus of the international community, leading to major changes in global energy technology.

[0003] As a new energy source with a wide range of sources, green, low-carbon, safe, efficient and renewable, hydrogen energy has gradually become an important tool for the development of energy transformation around the world with its high energy density and conversion efficiency. As an important green hydrogen production technology, the process of producing hydrogen by electrolysis of water uses electricity converted from renewable energy to produce hydrogen, which has broad market prospects in the future. Among them, alkaline water electrolysis is one of the more mature and commercialized hydrogen production technologies, with good economic benefits.

[0004] Diaphragms play an important role in alkaline water electrolysis devices. An ideal diaphragm needs to have high hydrogen and oxygen gas barrier efficiency, high ion conductivity and excellent alkali resistance and stability. Early diaphragms used polyphenylene sulfide (PPS) with good alkali resistance and stability, but there were problems such as low ion conductivity and high gas crossover risk. Although the anion exchange membrane (AEM) with a dense structure can achieve zero-spacing construction of the electrolyzer, its ion conductivity and alkali resistance are still difficult problems to overcome at present. The ion solvation membrane combines the advantages of early diaphragms and anion exchange membranes. It does not contain quaternary ammonium salt groups in its molecular structure, has strong alkali resistance and stability, and can operate in a strong alkaline electrolyte environment.

[0005] The main chain of polybenzimidazole (PBI) contains benzimidazole repeating units, which can be deprotonated by alkaline electrolytes and absorb alkaline solution to achieve ion transport. At the same time, it has high mechanical stability and thermal stability, making it one of the ideal materials for alkaline ion solvent membranes. However, a high concentration of alkaline environment will cause the imidazole ring to open and degrade, so its chemical stability needs to be further improved. At the same time, the conductivity of polybenzimidazole-based ion solvent membranes is still not ideal, resulting in low device performance. Therefore, designing the molecular structure of polybenzimidazole so that it absorbs more electrolytes to promote ion transport is of great significance for the development of alkaline ion solvent membranes. Summary of the invention

[0006] The purpose of the present invention is to provide a sterically hindered branched polybenzimidazole alkaline ion solvation membrane and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is to provide a method for preparing a sterically hindered branched polybenzimidazole polymer, comprising the following steps:

[0009] Under an inert atmosphere, 1 Polycarboxylic acid monomers with R 2 The dicarboxylic acid monomer of the structure is mixed with 3,3-diaminobenzidine and polyphosphoric acid, and mixed and reacted at 100-240° C. for 10-24 hours, and then the obtained mixed solution is added into deionized water, and the obtained solid matter is neutralized with alkali, washed to neutrality, and dried to obtain the hindered branched polybenzimidazole polymer;

[0010] Among them, R 1 Taken from one of the following structures:

[0011]

[0012] R 2 Taken from one or more of the following structures:

[0013]

[0014] In the present invention, R 1 Polycarboxylic acid monomers with R 2 There are many combinations of the order of adding the dicarboxylic acid monomer and 3,3-diaminobenzidine.

[0015] Furthermore, the preparation method of the above-mentioned sterically hindered branched polybenzimidazole polymer comprises the following steps: in an inert atmosphere, 2 The dicarboxylic acid monomer and 3,3-diaminobenzidine are added to the polyphosphoric acid aqueous solution, prepolymerized at 100-150°C for 0.5-3h, then cooled to 130°C, and R-containing 1 The polycarboxylic acid monomer of the structure and 3,3-diaminobenzidine are reacted at 130-240° C. for 3-24 hours, and then the obtained mixed solution is added into deionized water, and the obtained solid matter is neutralized with alkali, washed to neutrality, and dried to obtain the hindered branched polybenzimidazole polymer.

[0016] Furthermore, the polymer is immersed in a saturated sodium bicarbonate solution at 80° C. for 24 hours to neutralize the acidic substances in the polymer. The drying is preferably performed in a vacuum drying manner, the vacuum drying temperature is preferably 60-80° C., and the time is preferably 24-48 hours.

[0017] Furthermore, the R 1 Polycarboxylic acid monomers with R2 The mass ratio of the total mass of the dicarboxylic acid monomer and 3,3-diaminobenzidine to the polyphosphoric acid is 1:5-20; 1 The polycarboxylic acid monomer of structure and the R-containing 2 The molar ratio of the sum of the molar amounts of the carboxylic acid groups of the dicarboxylic acid monomers of the structure to the sum of the molar amounts of the amino groups of 3,3-diaminobenzidine is 1:2; 1 The total molar amount of carboxyl groups of the polycarboxylic acid monomers with the structure accounts for the total molar amount of carboxyl groups in the system (including R 1 The polycarboxylic acid monomers with R 2 The total carboxylic acid molar amount of the dicarboxylic acid monomers of the structure is 1% to 6%.

[0018] The second technical solution of the present invention is to provide a sterically hindered branched polybenzimidazole polymer prepared by the above preparation method. The obtained sterically hindered branched polybenzimidazole polymer is a random polymer or a block polymer.

[0019] Furthermore, the above-mentioned sterically hindered branched polybenzimidazole polymer has the general structure described in Formula I:

[0020]

[0021] The molecular weight of the sterically hindered branched polybenzimidazole polymer is 10000-120000, and the value of m is 10-100;

[0022] Among them, R 1 It is a multi-site branched structure; R 1 Taken from one of the following structures:

[0023]

[0024] R 2 Taken from one or more of the following structures:

[0025]

[0026] The third technical solution of the present invention is to provide another method for preparing a sterically hindered branched polybenzimidazole polymer, comprising the following steps: in an inert atmosphere, 1 Polycarboxylic acid monomers with R 2 Dicarboxylic acid monomers containing R 3 The dicarboxylic acid monomer of the structure and 3,3-diaminobenzidine are added to a polyphosphoric acid aqueous solution, mixed and reacted at 100-240° C. for 10-24 hours, and then the obtained mixed solution is added to deionized water, and the obtained solid matter is neutralized with alkali, washed to neutrality, and dried to obtain the sterically hindered branched polybenzimidazole polymer;

[0027] Among them, R1 Taken from one of the following structures:

[0028]

[0029] R 2 Taken from one or more of the following structures:

[0030]

[0031] R 3 One or more selected from the following structures:

[0032]

[0033] Furthermore, the preparation method of the above-mentioned sterically hindered branched polybenzimidazole polymer comprises the following steps: in an inert atmosphere, 2 Dicarboxylic acid monomers containing R 1 The polycarboxylic acid monomer and 3,3-diaminobenzidine are added to the polyphosphoric acid aqueous solution, prepolymerized at 100-150°C for 0.5-3h, then cooled to 130°C, and R-containing 3 The dicarboxylic acid monomer of the structure and 3,3-diaminobenzidine are reacted at 140-240° C. for 5-24 hours, and then the obtained mixed solution is added into deionized water, and the obtained solid matter is neutralized with alkali, washed to neutrality, and dried to obtain the hindered branched polybenzimidazole polymer.

[0034] Furthermore, the polymer is immersed in a saturated sodium bicarbonate solution at 80° C. for 24 hours to neutralize the acidic substances in the polymer. The drying is preferably performed in a vacuum drying manner, the vacuum drying temperature is preferably 60-80° C., and the time is preferably 24-48 hours.

[0035] Furthermore, the R 1 Polycarboxylic acid monomers with R 2 Dicarboxylic acid monomers containing R 3 The mass ratio of the total mass of the dicarboxylic acid monomer and 3,3-diaminobenzidine to the polyphosphoric acid is 1:4-20; 1 The polycarboxylic acid monomer of structure and the R-containing 2 , R 3 The molar ratio of the sum of the molar amounts of the carboxylic acid groups of the dicarboxylic acid monomers of the structure to the sum of the molar amounts of the amino groups of 3,3-diaminobenzidine is 1:2; 1 The total molar amount of carboxyl groups of the polycarboxylic acid monomers with the structure accounts for the total molar amount of carboxyl groups in the system (including R 1 Polycarboxylic acid monomers with R 2 Dicarboxylic acid monomers and R-containing 3The total molar amount of the dicarboxylic acid monomers of the structure) is 1% to 6%; containing R 2 The dicarboxylic acid monomers and R 3 The molar ratio of dicarboxylic acid monomers of the structure is 1:0-1, and R 3 The molar amount of the dicarboxylic acid monomer of the structure is not zero.

[0036] The fourth technical solution of the present invention is to provide a hindered branched polybenzimidazole polymer prepared by the above preparation method.

[0037] Furthermore, the above-mentioned sterically hindered branched polybenzimidazole polymer has a general structure shown in Formula II:

[0038]

[0039] The molecular weight of the sterically hindered branched polybenzimidazole polymer is 10000-120000, and the values ​​of n and q are 6-80 and 8-20 respectively;

[0041] Among them, R 1 Taken from one of the following structures:

[0042]

[0043] R 2 Taken from one or more of the following structures:

[0044]

[0045] R 3 One or more selected from the following structures:

[0046]

[0047] The fifth technical solution of the present invention is to provide a hindered branched polybenzimidazole alkaline ion solvation membrane, which is obtained by forming a membrane of the above-mentioned hindered branched polybenzimidazole polymer or another hindered branched polybenzimidazole polymer and then doping it with alkali.

[0048] The preparation method of the above-mentioned hindered branched polybenzimidazole alkaline ion solvation membrane comprises the following steps:

[0049] After the hindered branched polybenzimidazole polymer or the other hindered branched polybenzimidazole polymer is subjected to film-forming treatment, it is then immersed in alkaline solution to obtain the hindered branched polybenzimidazole alkaline ion solvation membrane.

[0050] Furthermore, the alkaline solution is one or more of potassium hydroxide solution, potassium carbonate solution, sodium hydroxide solution or sodium carbonate solution; the soaking temperature is 80° C., and the soaking time is 12-72 hours.

[0051] Furthermore, the film forming process is as follows: dissolving the sterically hindered branched polybenzimidazole polymer in a polar solvent, casting the obtained polymer solution on a plate (preferably a glass plate or a stainless steel plate), flattening it with a film casting knife, and drying it at 60-150° C. for 5-24 hours to obtain a sterically hindered branched polybenzimidazole polymer film. The thickness of the sterically hindered branched polybenzimidazole polymer film is 20-60 μm.

[0052] The polymer solution preferably has a solid content of 2-10 wt. %; the alkaline solution preferably has an alkali concentration of 1 wt. %-30 wt. %.

[0053] The organic solvent is a mixture of one or more of NMP, DMF, DMAc and DMSO.

[0054] Technical solution six of the present invention: providing the application of the above-mentioned hindered branched polybenzimidazole alkaline ion solvation membrane in alkaline water electrolysis tanks, zinc-air batteries, fuel cells or carbon dioxide electroreduction.

[0055] Furthermore, the electrolyte solute in new energy devices such as alkaline electrolytic cells, zinc-air batteries, and ammonia fuel cells is potassium hydroxide; the electrolyte concentration in the electrolytic cell device is preferably 1wt.%-30wt.%.

[0056] In the present invention, the characteristics of each group are as follows:

[0057] R 1 Structural characteristics of the group: The small volume rigid structure introduced as a branching agent can construct a light cross-linked structure, inhibit swelling, enhance the mechanical properties and alkali resistance of the polymer, and at the same time make the molecules in the membrane have a three-dimensional network structure, increase the free volume of the polymer, and improve the ionic conductivity.

[0058] R 2 Structural characteristics of the group: The introduction of a large rigid group can increase the steric hindrance of the C2 position of the imidazole group and enhance the alkali resistance and stability of the polymer.

[0059] R 3 Structural characteristics of the group: the introduction of hydrophilic auxiliary groups conducts negative ions through the action of acid-base ion pairs, accelerates ion conversion, and improves hydroxide conductivity, which mainly plays a role in improving the solubility and alkali absorption rate of the polymer.

[0060] The present invention designs the molecular structure of PBI, introduces steric structural units and branching sites into the PBI molecule to form a unique three-dimensional PBI structure, and can form a large number of open cavities in the membrane while maintaining alkali resistance stability, thereby improving the alkali doping level and maintaining good ion conductivity. In addition to being used in alkaline electrolyzers, the steric branched ion solvent membrane prepared by the present invention can also be extended to be used in new energy devices such as alkaline zinc-air batteries, ammonia fuel cells, and carbon dioxide electroreduction, and has good application prospects.

[0061] More specifically, after the hindered branched polybenzimidazole polymer of the present invention is soaked in an alkali solution, a portion of it exists in the polymer structure in the form of bound alkali, and a portion of it exists in the form of free alkali.

[0062] Take the solvent film after soaking in potassium hydroxide solution as an example:

[0063]

[0064] More preferably, the thickness of the ionic solvent film of the hindered branched polybenzimidazole polymer is 20-60 μm.

[0065] The performance test of the hindered branched polybenzimidazole ion solvent membrane of the present invention is carried out under the catalysis of pure nickel mesh foam, 1wt.%-30wt.% electrolyte (solute is potassium hydroxide), and 20-100°C through polarity curves under different current densities.

[0066] The present invention modifies the structure of the polybenzimidazole polymer, introduces a branch point of a rigid structure into the PBI to form a unique three-dimensional PBI structure, and forms a large number of open cavities in the membrane to improve the alkali doping level. The sterically hindered branched polybenzimidazole polymer of the present invention introduces a branched structure, so that the prepared ion solvent membrane has a larger microphase space, which is conducive to the construction of ion transmission channels.

[0067] The present invention discloses the following technical effects:

[0068] The synthesis conditions of the sterically hindered branched polybenzimidazole polymer of the present invention are mild and have a three-dimensional network structure. The ion solvent membrane constructed based on this type of polymer of the present invention is applied to new energy devices such as alkaline electrolyzers, zinc-air batteries, and ammonia fuel cells, and has excellent electrochemical performance and stability, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0070] Figure 1 This is a hydrogen nuclear magnetic resonance spectrum of the hindered branched polybenzimidazole polymer prepared in Example 1 of the present invention;

[0071] Figure 2 This is a hydrogen nuclear magnetic resonance spectrum of the hindered branched polybenzimidazole polymer prepared in Example 3 of the present invention;

[0072] Figure 3 This is a hydrogen nuclear magnetic resonance spectrum of the hindered branched polybenzimidazole polymer prepared in Example 5 of the present invention;

[0073] Figure 4 This is a hydrogen nuclear magnetic resonance spectrum of the hindered branched polybenzimidazole polymer prepared in Example 11 of the present invention;

[0074] Figure 5 The hydroxide conductivity of the hindered branched polybenzimidazole ion solvent membrane prepared in Examples 1-4 of the present invention;

[0075] Figure 6 Polarization curves of the hindered branched polybenzimidazole ion solvent membranes prepared in Examples 1-4 of the present invention and the linear polybenzimidazole ion solvent membrane prepared in Comparative Example 1 (referred to as Comparative Example) in an alkaline water electrolysis device. DETAILED DESCRIPTION

[0076] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0077] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0078] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0079] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0080] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0081] Example 1

[0082] Preparation of sterically branched polybenzimidazole ion solvent membrane with trimesic acid as branching structure:

[0083]

[0084] Here are the steps:

[0085] (1) Under nitrogen atmosphere, 40 g of polyphosphoric acid (PPA) solvent was added to a 100 mL three-necked flask, followed by 3,3-diaminobenzidine (10 mmol, 2.1427 g), 1,4-naphthalene dicarboxylic acid (9.57 mmol, 2.0689 g) and trimesic acid (0.3 mmol, 0.0631 g), heated to 180° C. with stirring for 24 h, and the solution was poured into deionized water while hot to obtain a flocculent polymer. After washing with deionized water for several times, the reaction system was adjusted to be neutral with a sodium bicarbonate solution, filtered, and the obtained solid polymer was boiled with water, filtered, and the obtained polymer NPBI-CO-H3BTC (branching degree of 3%) was dried;

[0086] (2) dissolving the polymer obtained after drying in step (1) in DMSO solvent to obtain a solid content of 2 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 60° C. for 24 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 40 μm (molecular weight of 40,000, and the value of m in the structural formula of 50);

[0087] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 10 wt.%) at 80° C. for 12 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0088] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 1 has an electrical conductivity of 0.190 S / cm in a 10 wt. % potassium hydroxide alkaline solution at 80° C.

[0089] Example 2

[0090] Preparation of sterically branched polybenzimidazole ion solvent membrane with trimesic acid as branching structure:

[0091]

[0092] Here are the steps:

[0093] (1) Under nitrogen atmosphere, 80 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (9.4 mmol, 2.0141 g) and 1,4-naphthalene dicarboxylic acid (9.1 mmol, 1.9673 g), heated and stirred to 120°C, and reacted for 0.5 h. Then, trimesic acid (0.6 mmol, 0.1261 g) and 3,3-diaminobenzidine (0.6 mmol, 0.1286 g) were added to the reaction system at 130°C, heated and stirred to 190°C, and reacted for 16 h. The solution was poured into deionized water while hot to obtain a flocculent polymer. The obtained polymer was washed with deionized water for several times, and the reaction system was adjusted to be neutral with sodium bicarbonate solution, filtered, and the obtained solid polymer was boiled. After filtering again, the obtained polymer NPBI-b-H3BTC (branching degree of 6%) was dried;

[0094] (2) dissolving the polymer obtained after drying in step (1) in DMF solvent to obtain a solid content of 3 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 70° C. for 20 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 35 μm (molecular weight of 50,000, and the value of m in the structural formula of 60);

[0095] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 20 wt.%) at 80° C. for 24 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0096] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 2 can achieve a conductivity of 0.200 S / cm in a 20 wt. % potassium hydroxide alkaline solution at 80° C.

[0097] Example 3

[0098] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of 1,3,5-(4-carboxyphenyl)benzene:

[0099]

[0100] Here are the steps:

[0101] (1) Under nitrogen atmosphere, 120 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (10 mmol, 2.1427 g), 1,4-naphthalene dicarboxylic acid (9.67 mmol, 2.0689 g) and 1,3,5-(4-carboxyphenyl)benzene (0.3 mmol, 0.1315 g), and the mixture was heated to 200° C. with stirring for 15 h. The solution was poured into deionized water while hot to obtain a flocculent polymer. After washing with deionized water for several times, the reaction system was adjusted to be neutral with a sodium bicarbonate solution, and the solid polymer was filtered and boiled with water, filtered, and the obtained polymer NPBI-CO-H3BTB (branching degree of 3%) was dried.

[0102] (2) dissolving the polymer obtained after drying in step (1) in DMAc solvent to obtain a solid content of 4 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 80° C. for 12 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 30 μm (molecular weight of 10,000, and m in the structural formula of 40);

[0103] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline sodium hydroxide solution (with a concentration of 30 wt.%) at 80° C. for 36 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0104] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 3 has an electrical conductivity of 0.208 S / cm in a 30 wt. % potassium hydroxide alkaline solution at 80° C.

[0105] Example 4

[0106] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of 1,3,5-(4-carboxyphenyl)benzene:

[0107]

[0108] Here are the steps:

[0109] (1) Under nitrogen atmosphere, 130 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (9.4 mmol, 2.0141 g) and 1,4-naphthalene dicarboxylic acid (9.1 mmol, 1.9673 g). The mixture was heated to 140° C. with stirring and reacted for 0.5 h. Then, 1,3,5-(4-carboxyphenyl)benzene (0.6 mmol, 0.26 30g) and 3,3-diaminobenzidine (0.6mmol, 0.1286g), heated and stirred to 210°C, reacted for 10h, poured the solution into deionized water while hot to obtain a flocculent polymer, washed the obtained polymer with deionized water for several times, adjusted the reaction system to be neutral with sodium bicarbonate solution, filtered, boiled the obtained solid polymer, filtered again, and dried the obtained polymer NPBI-b-H3BTB (branching degree of 6%);

[0110] (2) dissolving the polymer obtained after drying in step (1) in NMP solvent to obtain a solid content of 5 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 90° C. for 8 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film (molecular weight of 20,000, m value of 30) with a thickness of 45 μm;

[0111] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline sodium hydroxide solution (concentration of 30 wt.%) at 80° C. for 48 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0112] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 4 has an electrical conductivity of 0.220 S / cm in a 30 wt. % potassium hydroxide alkaline solution at 85° C.

[0113] Example 5

[0114] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of 1,3,5-(4-carboxyphenoxy)benzene:

[0115]

[0116] Here are the steps:

[0117] (1) Under nitrogen atmosphere, 120 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (10 mmol, 2.1427 g), 1,4-naphthalene dicarboxylic acid (9.67 mmol, 2.0689 g) and 1,3,5-tris(4-carboxyphenoxy)benzene (0.3 mmol, 0.1495 g), and the mixture was heated to 220° C. with stirring for 24 h. The solution was poured into deionized water while hot to obtain a flocculent polymer. After washing with deionized water for several times, the reaction system was adjusted to be neutral with a sodium bicarbonate solution, and the solid polymer was filtered and boiled with water, filtered, and the obtained polymer NPBI-CO-H3TCMB (branching degree of 3%) was dried;

[0118] (2) dissolving the polymer obtained after drying in step (1) in DMAc solvent to obtain a solid content of 5 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 100° C. for 5 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film (molecular weight of 80,000, m value of 70) with a thickness of 50 μm;

[0119] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 15 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0120] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 5 has an electrical conductivity of 0.220 S / cm in a 15 wt. % potassium hydroxide alkaline solution at 95° C.

[0121] Example 6

[0122] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of 1,3,5-(4-carboxyphenoxy)benzene:

[0123]

[0124] Here are the steps:

[0125] (1) Under nitrogen atmosphere, 130 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (9.4 mmol, 2.0141 g) and 1,4-naphthalene dicarboxylic acid (9.1 mmol, 1.9673 g). The mixture was heated to 140° C. with stirring and reacted for 0.5 h. Then, 1,3,5-tris(4-carboxyphenoxy)benzene (0.6 mmol, 0.0. 2990g) and 3,3-diaminobenzidine (0.6mmol, 0.1286g), heated with stirring to 230°C, reacted for 14h, poured the solution into deionized water while hot to obtain a flocculent polymer, washed the obtained polymer with deionized water for several times, adjusted the reaction system to be neutral with sodium bicarbonate solution, filtered, boiled the obtained solid polymer, filtered again, and dried the obtained polymer NPBI-b-H3TCMB (branching degree of 6%);

[0126] (2) dissolving the polymer obtained after drying in step (1) in NMP solvent to obtain a solid content of 6 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 85° C. for 11 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 50 μm (molecular weight of 70,000, and the value of m in the structural formula of 80);

[0127] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 16 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0128] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 6 has an electrical conductivity of 0.198 S / cm in a 16 wt. % potassium hydroxide alkaline solution at 90° C.

[0129] Example 7

[0130] Preparation of sterically branched polybenzimidazole ionic solvent membrane with tris-discene-2,4,6-tricarboxylic acid as branched structure:

[0131]

[0132] Here are the steps:

[0133] (1) Under nitrogen atmosphere, 45 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (2.12 mmol, 0.4543 g), 1,4-naphthalene dicarboxylic acid (1.64 mmol, 0.3545 g) and tris-discene-2,4,6-tricarboxylic acid (0.24 mmol, 0.0927 g). The mixture was heated to 130 °C with stirring and reacted for 0.5 h. Then, 4,4'-dihydro-1-nitropropene was added to the reaction system at 130 °C. Phenyl ether dicarboxylic acid (2.12mmol, 0.5474g) and 3,3-diaminobenzidine (2mmol, 0.5814g) were heated to 230°C with stirring and reacted for 3 hours. The solution was poured into deionized water while hot to obtain a flocculent polymer. The obtained polymer was washed with deionized water for several times, and the reaction system was adjusted to be neutral with sodium bicarbonate solution, filtered, and the obtained solid polymer was boiled, filtered again, and the polymer TP-NPBI-CO-OPBI was dried;

[0134] (2) dissolving the polymer obtained after drying in step (1) in DMSO solvent to make the solid content 10 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 80° C. for 20 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 20 μm (molecular weight of 30,000, and the values ​​of n and q in the structural formula are 20 and 10, respectively);

[0135] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 10 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0136] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 7 has an electrical conductivity of 0.188 S / cm in a 10 wt. % potassium hydroxide alkaline solution at 80° C.

[0137] Example 8

[0138] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of pyridine-2,4,6-tricarboxylic acid:

[0139]

[0140] Here are the steps:

[0141] (1) Under nitrogen atmosphere, 45 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (2.12 mmol, 0.4543 g), 9,10-anthracene dicarboxylic acid (1.64 mmol, 0.4367 g) and pyridine-2,4,6-tricarboxylic acid (0.24 mmol, 0.0567 g). The mixture was heated to 150° C. and stirred for 0.5 h. Then, pyridine-2,4,6-tricarboxylic acid was added to the reaction system at 130° C. 6-dicarboxylic acid (2.12mmol, 0.3543g) and 3,3-diaminobenzidine (2mmol, 0.4285g), heated to 200°C with stirring, reacted for 23 hours, poured the solution into deionized water while hot to obtain a flocculent polymer, washed the obtained polymer with deionized water for several times, adjusted the reaction system to neutrality with sodium bicarbonate solution, filtered, boiled the obtained solid polymer, filtered again and dried the polymer P-APBI-co-pPBI;

[0142] (2) dissolving the polymer obtained after drying in step (1) in DMF solvent to obtain a solid content of 8 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 90° C. for 14 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 60 μm (molecular weight of 60,000, and the values ​​of n and q in the structural formula are 30 and 12, respectively);

[0143] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline solution (with a concentration of 6 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0144] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 8 has a conductivity of 0.206 S / cm in a 6 wt. % alkaline solution at 95° C.

[0145] Example 9

[0146] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine:

[0147]

[0148] Here are the steps:

[0149] (1) Under nitrogen atmosphere, 45 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (2.12 mmol, 0.4543 g), 2,6-naphthalene dicarboxylic acid (1.64 mmol, 0.0266 g) and 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine (0.24 mmol, 0.085 g). The mixture was heated to 140°C with stirring for 0.5 h. Then, the reaction system was added at 130°C. Add sodium 5-sulfonate of terephthalic acid (2.12 mmol, 0.5728 g) and 3,3-diaminobenzidine (2 mmol, 0.4285 g), heat and stir to 210°C, react for 19 hours, pour the solution into deionized water while hot to obtain a flocculent polymer, wash the obtained polymer with deionized water for several times, adjust the reaction system to neutrality with sodium bicarbonate solution, filter, boil the obtained solid polymer, filter again and dry the polymer Ta-NPBI-CO-SPBI;

[0150] (2) dissolving the polymer obtained after drying in step (1) in DMAc solvent to obtain a solid content of 9 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 70° C. for 18 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 55 μm (molecular weight of 90,000, and the values ​​of n and q in the structural formula are 40 and 14, respectively);

[0151] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 15 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0152] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 9 can achieve a conductivity of 0.205 S / cm in a 15 wt. % potassium hydroxide alkaline solution at 80° C.

[0153] Example 10

[0154] Preparation of sterically branched polybenzimidazole ion solvent membrane with branched structure of 4,4'4"-triphenylamine tricarboxylate:

[0155]

[0156] Here are the steps:

[0157] (1) Under nitrogen atmosphere, 45 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (2.12 mmol, 0.4543 g), 9,10-anthracene dicarboxylic acid (1.64 mmol, 0.4367 g) and 4,4'4"-triphenylamine tricarboxylate (0.24 mmol, 0.0910 g). The mixture was heated to 140° C. with stirring and reacted for 0.5 h. Then, 3,3'-dihydroxy-[1, 1'-biphenyl]-4,4'-dicarboxylic acid (2.12mmol, 0.4711g) and 3,3-diaminobenzidine (2mmol, 0.5814g), heated and stirred to 230°C, reacted for 3h, poured the solution into deionized water while hot to obtain a flocculent polymer, washed the obtained polymer with deionized water for several times, adjusted the reaction system to neutrality with sodium bicarbonate solution, filtered, boiled the obtained solid polymer, filtered again and dried the polymer N-APBI-CO-oPBI;

[0158] (2) dissolving the polymer obtained after drying in step (1) in DMF solvent to make the solid content 10 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 80° C. for 20 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 20 μm (molecular weight of 100,000, and the values ​​of n and q in the structural formula are 50 and 16, respectively);

[0159] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 9 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0160] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 10 can achieve a conductivity of 0.189 S / cm in a 9 wt. % potassium hydroxide alkaline solution at 85° C.

[0161] Embodiment 11

[0162] Preparation of sterically branched polybenzimidazole ion solvent membrane with trimesic acid as branching monomer:

[0163]

[0164] Here are the steps:

[0165] (1) Under nitrogen atmosphere, 120 g of polyphosphoric acid solvent was added to a 250 mL three-necked flask, followed by 3,3-diaminobenzidine (10 mmol, 2.1427 g), 1,4-naphthalene dicarboxylic acid (8.703 mmol, 1.86201 g), trimesic acid (0.3 mmol, 0.1495 g), and 2-sulfonatoterephthalic acid (0.967 mmol, 2.6817 g). The mixture was heated to 240° C. with stirring for 10 h. The solution was poured into deionized water while hot to obtain a flocculent polymer. After washing with deionized water for several times, the reaction system was adjusted to be neutral with a sodium bicarbonate solution, and the solid polymer obtained was filtered and boiled with water, filtered, and the obtained polymer H3BTC-NPBI-b-SPBI was dried;

[0166] (2) dissolving the polymer obtained after drying in step (1) in DMAc solvent to obtain a solid content of 5 wt.%, casting the obtained polymer solution directly on a glass plate, flattening it with a film casting knife, and drying it at 100° C. for 5 h to form a film, thereby obtaining a sterically branched polybenzimidazole polymer film with a thickness of 50 μm (molecular weight of 110,000, and the values ​​of n and q in the structural formula of 60 and 18, respectively);

[0167] (3) The hindered branched polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 15 wt.%) at 80° C. for 72 hours to obtain a hindered branched polybenzimidazole ion solvent membrane.

[0168] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 11 can achieve a conductivity of 0.240 S / cm in a 15 wt. % potassium hydroxide alkaline solution at 95° C.

[0169] Comparative Example 1

[0170] Preparation of a linear polybenzimidazole ion solvent membrane:

[0171]

[0172] Among them, m is 500.

[0173] Here are the steps:

[0174] (1) In a nitrogen atmosphere, add 30 g of polyphosphoric acid to a 100 mL three-necked flask, heat to 100 °C, and mechanically stir for several hours to obtain a colorless transparent liquid. Then add 3,3-diaminobenzidine (1.0713 g), add isophthalic acid (0.0831 g) after dissolving, program the temperature to 140 °C and react for 7 hours, pour the solution into deionized water while hot to obtain a filamentous polymer, wash it with deionized water several times, adjust it to neutral with sodium bicarbonate solution, filter and boil the obtained solid polymer with water, filter and dry the obtained polymer;

[0175] (2) dissolving the dried polymer in NMP solvent to a solid content of 2 wt.%, casting the obtained polymer solution on a glass plate after centrifugation, flattening it with a film casting knife, and drying it at 80° C. for 20 h to form a film with a thickness of 55 μm;

[0176] (3) The linear polybenzimidazole polymer membrane prepared in step (2) is immersed in an alkaline potassium hydroxide solution (with a concentration of 9 wt.%) at 80° C. for 72 hours to obtain a linear polybenzimidazole ion solvent membrane.

[0177] Effect verification example 1

[0178] The mechanical properties of the hindered branched polybenzimidazole ion solvent membranes prepared in Examples 1-11 and the linear polybenzimidazole ion solvent membrane prepared in Comparative Example 1 were compared. The results are shown in Table 1.

[0179] Table 1

[0180] project Tensile strength / MPa Elongation at break / % Comparative Example 1 102.4 35.3 Example 1 118.8 25.5 Example 2 144.6 16.1 Example 3 152.4 21.2 Example 4 144.6 11.1 Example 5 138.2 13.8 Example 6 132.5 22.4 Example 7 153.2 26.8 Example 8 144.5 10.5 Example 9 137.6 26.2 Example 10 143.7 15.9 Embodiment 11 145.8 23.9

[0181] The sterically hindered branched polybenzimidazole ion solvent membrane prepared by the invention has excellent tensile strength.

[0182] Effect verification example 2

[0183] The hindered branched polybenzimidazole ion solvent membrane prepared in Example 1 and the membrane material prepared in Comparative Example 1 were used in an alkaline water electrolysis tank device for performance verification. The steps are as follows:

[0184] (1) Preparation of membrane electrode assembly for water electrolysis device:

[0185] Pure nickel mesh foam was used for both cathode and anode. The pure nickel mesh foam was placed in a hot press machine and hot pressed at 120°C for 5 minutes before being taken out. Then, the membrane material prepared in Example 1 or Comparative Example 1 was sandwiched between two nickel mesh foam electrodes to obtain a membrane electrode assembly with an effective area of ​​4 cm 2 ;

[0186] (2) The membrane electrode assembly was sandwiched between the cathode and the anode to assemble a water electrolysis device, and the electrochemical test was carried out in a 25 wt.% KOH electrolyte at 80° C. The polarization curve was obtained by measuring the cell voltage at different current densities.

[0187] like Figure 6 As shown, in a 25wt.% potassium hydroxide solution, the test was carried out at 80°C. The results showed that the performance of the ion solvent membrane prepared in Example 1 was significantly better than that of the membrane material in Comparative Example 1. At 1.8V, the current density could reach 3.5A / cm -2, indicating that the introduction of branched structure increases the alkali doping content of the membrane and forms microphase separation channels, providing a convenient pathway for ion transport.

[0188] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a sterically hindered branched polybenzimidazole polymer, characterized in that: The following steps are involved: In an inert atmosphere, a polycarboxylic acid monomer containing an R1 structure, a dicarboxylic acid monomer containing an R2 structure, 3,3-diaminobenzidine and polyphosphoric acid are mixed, and the mixture is reacted at 100-240° C. for 10-24 hours, and then the obtained mixed solution is added into deionized water, and the obtained solid matter is neutralized with an alkali, washed to neutrality, and dried to obtain the hindered branched polybenzimidazole polymer; Wherein, R1 is selected from one of the following structures: R2 is selected from one or more of the following structures:

2. The preparation method according to claim 1, characterized in that: The mass ratio of the total mass of the polycarboxylic acid monomer containing the R1 structure, the dicarboxylic acid monomer containing the R2 structure and 3,3-diaminobenzidine to polyphosphoric acid is 1:5-20; the molar ratio of the sum of the molar amounts of the carboxylic acid groups of the polycarboxylic acid monomer containing the R1 structure and the dicarboxylic acid monomer containing the R2 structure to the sum of the molar amounts of the amino groups of 3,3-diaminobenzidine is 1:2; and the total molar amount of carboxyl groups of the polycarboxylic acid monomer containing the R1 structure accounts for 1%-6% of the total molar amount of carboxyl groups in the system.

3. The hindered branched polybenzimidazole polymer prepared by the preparation method according to any one of claims 1 to 2.

4. The sterically hindered branched polybenzimidazole polymer according to claim 3, characterized in that: It has the general structure described in Formula I: The molecular weight of the sterically hindered branched polybenzimidazole polymer is 10000-120000, and the value of m is 10-100; Wherein, R1 is selected from one of the following structures: R2 is selected from one or more of the following structures:

5. A method for preparing a sterically hindered branched polybenzimidazole polymer, characterized in that: The following steps are involved: Under an inert atmosphere, a polycarboxylic acid monomer containing an R1 structure, a dicarboxylic acid monomer containing an R2 structure, a dicarboxylic acid monomer containing an R3 structure and 3,3-diaminobenzidine are added to a polyphosphoric acid aqueous solution, mixed and reacted at 100-240° C. for 10-24 hours, and then the obtained mixed solution is added to deionized water, and the obtained solid matter is neutralized with an alkali, washed to neutrality, and dried to obtain the hindered branched polybenzimidazole polymer; Wherein, R1 is selected from one of the following structures: R2 is selected from one or more of the following structures: R3 is selected from one or more of the following structures:

6. The preparation method according to claim 5, characterized in that: The mass ratio of the total mass of the polycarboxylic acid monomer containing R1 structure, the dicarboxylic acid monomer containing R2 structure, the dicarboxylic acid monomer containing R3 structure and 3,3-diaminobenzidine to polyphosphoric acid is 1:5-20; the molar ratio of the sum of the molar amounts of the carboxylic acid groups of the polycarboxylic acid monomer containing R1 structure and the dicarboxylic acid monomer containing R2 and R3 structures to the sum of the molar amounts of the amino groups of 3,3-diaminobenzidine is 1:2; the total molar amount of carboxyl groups of the polycarboxylic acid monomer containing R1 structure accounts for 1%-6% of the total molar amount of carboxyl groups in the system; the molar ratio of the dicarboxylic acid monomer containing R2 structure and the dicarboxylic acid monomer containing R3 structure is 1:0-1, and the molar amount of the dicarboxylic acid monomer containing R3 structure is not 0.

7. The hindered branched polybenzimidazole polymer prepared by the preparation method according to any one of claims 5 to 6.

8. The hindered branched polybenzimidazole polymer according to claim 7, characterized in that: It has the general structure shown in Formula II: The molecular weight of the sterically hindered branched polybenzimidazole polymer is 10,000-120,000, and the values ​​of n and q are 6-80 and 8-20 respectively; Wherein, R1 is selected from one of the following structures: R2 is selected from one or more of the following structures: R3 is selected from one or more of the following structures:

9. A sterically hindered branched polybenzimidazole alkaline ion solvation membrane, characterized in that: The sterically hindered branched polybenzimidazole polymer according to claim 3 or the sterically hindered branched polybenzimidazole polymer according to claim 7 is formed into a film and then doped with alkali.

10. Use of the hindered branched polybenzimidazole alkaline ion solvation membrane according to claim 9 in an alkaline water electrolysis tank, a zinc-air battery, a fuel cell or carbon dioxide electroreduction.

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