Integrated polybenzimidazole gradient membranes, methods of making and using the same

Abstract

The application discloses an integrated polybenzimidazole gradient membrane and a preparation method and application thereof. The preparation method comprises the following steps: applying a first solution containing polybenzimidazole, a polar solvent and a small-molecule sacrificial template to a substrate surface, removing the polar solvent, forming a dense small-molecule solvated polymer support layer, applying a second solution containing polybenzimidazole and a polar solvent to the surface of the small-molecule solvated polymer support layer, removing the polar solvent to form a screening layer, and fusing the small-molecule solvated polymer support layer and the screening layer to form an integrated structure, thereby obtaining an integrated polybenzimidazole membrane. In-situ etching treatment is performed to obtain an integrated polybenzimidazole gradient membrane. According to the application, a high-selectivity separation thin layer is constructed on the surface of the polymer support layer, the hydrophilic narrow ion channel size can ensure ion screening, the trade-off effect of conductivity and selectivity is broken through, and the membrane has high ion conductivity, high mechanical property, high ion selectivity and high stability.

Description

Technical Field

[0001] This invention relates to a polybenzimidazole membrane, specifically to an integrated polybenzimidazole gradient membrane and its preparation method and application, belonging to the field of ion exchange membrane technology. Background Technology

[0002] To actively address global climate change, reduce greenhouse gas emissions, and achieve sustainable development, renewable energy conversion technologies such as flow batteries, fuel cells, and water electrolysis for hydrogen production play a crucial role in achieving the "dual carbon" goals, driving the energy structure shift from reliance on fossil fuels to clean energy and reducing environmental pollution. Among these technologies, ion exchange membranes, as key components in renewable energy conversion equipment such as fuel cells, flow batteries, and water electrolysis for hydrogen production, play a vital role in selectively conducting ions and blocking electrons, and are a material that my country urgently needs to develop. Currently, commercially available flow batteries commonly use perfluorosulfonic acid ion exchange membranes (such as Nafion), which have high ion conductivity and excellent tolerance, and are widely used in renewable energy conversion equipment. However, due to their low selective permeability, hydrogen permeation occurs when used in fuel cells or water electrolysis for hydrogen production, and ion cross-contamination easily occurs when used in flow batteries, limiting their commercial application in renewable energy conversion equipment. Although modifying perfluorosulfonic acid membranes can significantly improve selective permeability, the sheet resistance of the membrane usually increases, and the high cost of perfluorosulfonic acid membranes has not been solved, making it difficult for modified perfluorosulfonic acid membranes to meet the needs of large-scale commercial applications. This makes high-performance, low-cost ion exchange membranes key to determining the efficiency and lifespan of renewable energy conversion equipment.

[0003] Traditional polymeric ion-exchange membrane materials rely on microscale phase separation, making it difficult to simultaneously achieve high ion conductivity and high ion selectivity. Therefore, there is an urgent need to develop novel membrane materials to improve ion-selective conduction. Polybenzimidazole (PBI) membranes have attracted widespread attention due to their excellent ion separation performance and superior stability under harsh conditions. They can be prepared by monomer condensation and cyclization of corresponding diamines and carboxylic acids. PBI membranes exhibit absorption capacity for inorganic acids and can achieve ion conduction even with acid doping. However, the low degree of microphase separation within homogeneous membranes results in only angstrom-sized ion channels, leading to low ion conductivity. Therefore, designing the microstructure of PBI membrane ion conduction channels and controlling the ion-selective conduction process are crucial for improving their performance. Summary of the Invention

[0004] The main objective of this invention is to provide an integrated polybenzimidazole gradient membrane and its preparation method, so as to overcome the shortcomings of the prior art.

[0005] Another object of the present invention is to provide the application of the integrated polybenzimidazole gradient membrane.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention also provides a method for preparing an integrated polybenzimidazole gradient film, comprising:

[0008] A first solution containing polybenzimidazole, a polar solvent, and a small molecule sacrificial template soluble in organic solvents is applied to the surface of a substrate. The polar solvent is removed by heating, and a dense small molecule solvated polymer support layer is formed. In the first solution, the total mass of the small molecule sacrificial template and the polybenzimidazole is calculated as 100%, and the mass percentage of the small molecule sacrificial template is 1-95%.

[0009] A second solution containing polybenzimidazole and a polar solvent is applied to the surface of the small molecule solvated polymer support layer. The polar solvent is removed by heating, and a sieve layer is formed on the surface of the small molecule solvated polymer support layer. At least a portion of the polybenzimidazole on the side of the small molecule solvated polymer support layer in contact with the sieve layer is interfused with the polybenzimidazole in the sieve layer to form an integrated structure, thereby obtaining an integrated polybenzimidazole membrane. In the second solution, the mass ratio of the polybenzimidazole to the volume of the polar solvent is 1~30 g / mL.

[0010] The integrated polybenzimidazole film is etched in situ with an etchant to remove the small molecule sacrificial template in the small molecule solvated polymer support layer, thereby obtaining the integrated polybenzimidazole gradient film.

[0011] This invention provides an integrated polybenzimidazole gradient membrane prepared by the aforementioned method, comprising:

[0012] The polybenzimidazole support layer has wide and interconnected ion channels;

[0013] A dense polybenzimidazole sieve layer is stacked on the surface of the polybenzimidazole support layer, having narrow and interconnected angstrom-level channels;

[0014] In this structure, at least a portion of the polybenzimidazole on the side of the polybenzimidazole support layer in contact with the sieve layer is fused with the polybenzimidazole in the sieve layer to form an integrated structure. Along the thickness direction of the integrated polybenzimidazole gradient film, the size gradient of the channel structure contained in the polybenzimidazole support layer decreases from the polybenzimidazole support layer to the polybenzimidazole sieve layer. The ion channel size of the polybenzimidazole support layer is in the angstrom to nanometer range, and the thickness of the polybenzimidazole sieve layer is 0.1~10µm.

[0015] Accordingly, embodiments of the present invention also provide the application of the integrated polybenzimidazole gradient membrane in renewable energy conversion equipment.

[0016] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0017] 1) This invention constructs a highly selective separation thin layer along the film thickness direction by spin-coating a polybenzimidazole solution onto the surface of a small molecule solvated polymer support layer. The size of its hydrophilic narrow ion channel ensures accurate ion sieving and is integrated with the high conductivity small molecule solvated polymer support layer. Then, the small molecule sacrificial template is removed by in-situ etching to construct a cascade mass transfer channel, which synergistically overcomes the trade-off effect of conductivity and selectivity, and achieves a balance of "high conductivity + high selectivity".

[0018] 2) The preparation process of the present invention is simple, easy to industrialize, and low in cost. The integrated polybenzimidazole gradient membrane prepared has high ion conductivity, high mechanical properties, high ion selectivity and high stability, which is suitable for the application requirements of renewable energy conversion equipment. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a morphology characterization image of the integrated polybenzimidazole gradient film obtained in Example 1 of the present invention, wherein... Figure 1 (a) is a cross-sectional SEM image of the integrated polybenzimidazole gradient membrane obtained in Example 1 of the present invention. Figure 1 (b) is a magnified SEM image of the polybenzimidazole support layer in the integrated polybenzimidazole gradient membrane obtained in Example 1 of the present invention;

[0021] Figure 2 This is a TEM image of the polybenzimidazole sieve layer in the integrated polybenzimidazole gradient membrane obtained in Example 1 of the present invention;

[0022] Figure 3 and Figure 4 These are graphs showing the cycling data and long-term cycling data of the flow battery with the integrated polybenzimidazole gradient membrane obtained in Example 1 of the present invention at different current densities.

[0023] Figure 5 and Figure 6 These are the polarization curves and long-term life test data of the fuel cell with the integrated polybenzimidazole gradient membrane obtained in Example 1 of the present invention.

[0024] Figure 7 and Figure 8These are the polarization curves and lifetime test diagrams of the integrated polybenzimidazole gradient membrane obtained in Example 1 of this invention for hydrogen production by water electrolysis.

[0025] Figure 9 and Figure 10 These are the cycle data and lifetime test graphs of the integrated polybenzimidazole gradient membrane flow battery obtained in Example 2 of the present invention under different current densities. Detailed Implementation

[0026] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. Primarily, from the perspective of molecular structure design, an integrated polybenzimidazole gradient membrane design is proposed. Using polybenzimidazole membrane material with narrow ion hydrophilic channels as the matrix, a small molecule sacrificial template is used to connect with the polybenzimidazole polymer chain through multiple hydrogen bonds or coordination interactions, inducing the formation of pseudo-phase separation channels. This constructs a small molecule solvated polymer support layer with high conductivity and high mechanical properties, and an in-situ composite polybenzimidazole sieve thin layer of controllable thickness is then added. Finally, the small molecule sacrificial template is removed by in-situ etching, constructing a tiered mass transfer channel and synergistically overcoming the trade-off effect in conductivity and selectivity.

[0027] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0028] As one aspect of the technical solution of this invention, the preparation method of an integrated polybenzimidazole gradient membrane mainly involves: using a polybenzimidazole membrane material with hydrophilic narrow ion channels as a matrix, using a small molecule sacrificial template, connecting it to the polybenzimidazole polymer chain through multiple hydrogen bonds or coordination interactions, inducing the formation of pseudo-phase separation channels, constructing a small molecule solvated polymer support layer with high conductivity and high mechanical properties, and in-situ composite a polybenzimidazole sieved thin layer of controllable thickness, and finally removing the small molecule sacrificial template by in-situ etching to construct a cascade mass transfer channel.

[0029] In some embodiments, the method for preparing the integrated polybenzimidazole gradient film specifically includes:

[0030] A first solution containing polybenzimidazole, a polar solvent, and a small molecule sacrificial template soluble in organic solvents is applied to the surface of a substrate. The polar solvent is removed by heating, and a dense small molecule solvated polymer support layer is formed. In the first solution, the total mass of the small molecule sacrificial template and the polybenzimidazole is calculated as 100%, and the mass percentage of the small molecule sacrificial template is 1-95%.

[0031] A second solution containing polybenzimidazole and a polar solvent is applied to the surface of the small molecule solvated polymer support layer. The polar solvent is removed by heating, and a sieve layer is formed on the surface of the small molecule solvated polymer support layer. At least a portion of the polybenzimidazole on the side of the small molecule solvated polymer support layer in contact with the sieve layer is interfused with the polybenzimidazole in the sieve layer to form an integrated structure, thereby obtaining an integrated polybenzimidazole membrane. In the second solution, the mass ratio of the polybenzimidazole to the volume of the polar solvent is 1~30 g / mL.

[0032] The integrated polybenzimidazole film is etched in situ with an etchant to remove the small molecule sacrificial template in the small molecule solvated polymer support layer, thereby obtaining the integrated polybenzimidazole gradient film.

[0033] In some preferred embodiments, the small molecule sacrificial template selected in this invention is an organic solvent-soluble molecule that forms a homogeneous and transparent solution when blended. Specifically, the small molecule sacrificial template may include one or more of the following combinations: ferrous chloride, ferric chloride, chromium chloride, zinc chloride, polyethylene glycol, polyethyleneimine, 15-crown ether-5, 18-crown ether-6, benzo-15-crown ether-5, dibenzo-18-crown ether-6, diethylene glycol diethyl ether, etc., but is not limited thereto.

[0034] In some preferred embodiments, the polar solvent may include one or more combinations of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and methanesulfonic acid, but is not limited thereto.

[0035] In some preferred embodiments, in the first solution, the sum of the mass of the small molecule sacrificial template and the polybenzimidazole is calculated as 100%, the mass percentage of the small molecule sacrificial template is 20-80%, and the remainder is polybenzimidazole.

[0036] In some preferred embodiments, in the first solution, the ratio of the sum of the mass of the small molecule sacrificial template and the polybenzimidazole to the volume of the polar solvent is 1~95 g / mL, preferably 10~60 g / mL.

[0037] In some preferred embodiments, the preparation method specifically includes: first dissolving polybenzimidazole in a polar solvent to form a polymer solution, then adding a small molecule sacrificial template to the polymer solution, and mixing thoroughly by ultrasound or stirring to obtain the first solution.

[0038] In some preferred embodiments, the mass ratio of the polybenzimidazole to the volume of the polar solvent in the second solution is 10-25 g / mL.

[0039] In some preferred embodiments, the preparation method specifically includes: dissolving polybenzimidazole in a polar solvent and mixing thoroughly by ultrasound or stirring to obtain the second solution.

[0040] In some preferred embodiments, the method of removing the polar solvent by heating includes drying at 40~120°C for 1~48 hours.

[0041] In some preferred embodiments, the preparation method specifically includes: applying the first solution to the surface of a substrate using at least a casting method or a coating method.

[0042] In some preferred embodiments, the preparation method specifically includes: applying the second solution to the surface of the small molecule solvated polymer support layer by at least casting or scraping.

[0043] In some preferred embodiments, the etching agent may include at least one of dilute hydrochloric acid, dilute sulfuric acid, aqueous phosphoric acid solution, aqueous lithium hydroxide solution, aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, aqueous lithium chloride solution, aqueous sodium chloride solution, aqueous potassium chloride solution, aqueous ammonium chloride solution, water, etc., but is not limited thereto.

[0044] Further, the etching agent may include at least one of the following: 0.1-3 mol / L dilute hydrochloric acid, 0.1-3 mol / L dilute sulfuric acid, 10-85 wt% phosphoric acid aqueous solution, 0.1-6 mol / L lithium hydroxide aqueous solution, 0.1-6 mol / L sodium hydroxide aqueous solution, 0.1-6 mol / L potassium hydroxide aqueous solution, 0.1-3 mol / L lithium chloride aqueous solution, 0.1-3 mol / L sodium chloride aqueous solution, 0.1-3 mol / L potassium chloride aqueous solution, and 0.1-3 mol / L ammonium chloride aqueous solution, but is not limited thereto.

[0045] In some preferred embodiments, the preparation method specifically includes: immersing the integrated polybenzimidazole film in an etchant to perform the in-situ etching treatment, wherein the immersion temperature is room temperature to 100°C and the immersion time is more than 5 hours.

[0046] In some preferred embodiments, the preparation method may further include: after the in-situ etching process is completed, washing away the residual etching agent on the surface of the integrated polybenzimidazole gradient film with water for more than 1 hour until the residual substances in the film are completely washed away.

[0047] Furthermore, the preparation method may further include: repeating the in-situ etching process and the etchant removal steps more than twice until the small molecule sacrificial template is completely washed away.

[0048] In some more specific preferred embodiments, the preparation method of the integrated polybenzimidazole gradient film specifically includes the following steps:

[0049] (1) Dissolve polybenzimidazole in a polar solvent, then disperse the small molecule sacrificial template into the obtained polymer solution, mix thoroughly and filter, then form a film on the substrate by casting or scraping, and heat to remove the polar solvent to obtain a dense small molecule solvated polymer support layer.

[0050] (2) After fully dissolving polybenzimidazole in a polar solvent, coat it onto the small molecule solvated polymer support layer obtained in step (1), heat the integrated small molecule solvated polymer support layer and the polybenzimidazole sieve layer, and remove the polar solvent to obtain an integrated polybenzimidazole membrane containing a polybenzimidazole sieve thin layer.

[0051] (3) Immerse the integrated polybenzimidazole membrane obtained in step (2) in an etchant for a certain time to remove the small molecule sacrificial template, and then wash it with water to remove the residual etchant to obtain the integrated polybenzimidazole gradient membrane.

[0052] Furthermore, in step (1), during the mixing process of the small molecule sacrificial template and polybenzimidazole, the mixture is uniformly dispersed and fully mixed by ultrasound or stirring.

[0053] Furthermore, in step (2), during the dissolution of the polybenzimidazole, it is uniformly dispersed and fully mixed by ultrasound or stirring.

[0054] The mechanism of the integrated polybenzimidazole membrane prepared by this invention is as follows: First, by uniformly dispersing a small molecule sacrificial template within the polybenzimidazole matrix membrane, the pseudo-microphase separation within the membrane can be regulated through multiple hydrogen bonds or coordination interactions, controlling the structure and morphology of the ion channels. This can be arbitrarily adjusted as needed at the nanometer to micrometer scale, constructing a dense small molecule solvated polymer support layer with high conductivity and high mechanical properties (ensuring conductivity). Second, a polybenzimidazole solution is spin-coated onto the surface of the small molecule solvated polymer support layer, constructing a highly selective separation thin layer along the membrane thickness direction. Its hydrophilic narrow ion channel size ensures precise ion sieving (ensuring ion selectivity). The sieving layer is a dense PBI layer with narrow and interconnected angstrom-level channels (<1 nm). Through the size repulsion effect, it selectively conducts target ions, blocking large-sized ions or molecules, and integrates with the small molecule solvated polymer support layer. Then, the small molecule sacrificial template is removed by in-situ etching, overcoming the trade-off effect between conductivity and selectivity. The two work together to achieve a balance of "high conductivity + high selectivity". The small molecule solvated polymer support layer can form a continuous pore structure after etching, creating wide and interconnected pore channels, improving ion conductivity, and consequently increasing the coulombic efficiency of the battery.

[0055] Furthermore, the sieve layer and the support layer form an integrated structure through "fusion," avoiding the interlayer interface resistance of traditional composite membranes and reducing ion conduction losses. The dense structure of the sieve layer provides surface protection for the support layer, reducing the brittleness of the porous support layer and improving the overall tensile strength and bending resistance of the membrane. Moreover, the dense structure of the sieve layer effectively inhibits electrolyte cross-contamination and gas permeation, overcoming the defect of easy permeation in the porous structure of polybenzimidazole membranes in existing technologies.

[0056] This invention mainly regulates and optimizes ion-selective conduction by controlling the structure, ratio, and interaction of the small molecule sacrificial template and polybenzimidazole polymer in the support layer, as well as the structure and thickness of the polybenzimidazole polymer in the sieve layer. This results in a membrane with high ion conductivity, high mechanical properties, high ion selectivity, and high stability, thereby improving its efficiency and durability in renewable energy conversion equipment.

[0057] As another aspect of the technical solution of this invention, it also relates to an integrated polybenzimidazole gradient membrane, which is prepared by the above-described preparation method. In the integrated polybenzimidazole gradient membrane prepared by this invention, the pore size, pore morphology, pore diameter distribution, and pore connectivity of the polybenzimidazole support layer and the polybenzimidazole sieve layer can all be separately controlled.

[0058] Specifically, the integrated polybenzimidazole gradient membrane includes:

[0059] The polybenzimidazole support layer has wide and interconnected ion channels;

[0060] A dense polybenzimidazole sieve layer is stacked on the surface of the polybenzimidazole support layer, having narrow and interconnected angstrom-level channels;

[0061] In this structure, at least a portion of the polybenzimidazole on the side of the polybenzimidazole support layer that contacts the sieve layer is fused with the polybenzimidazole in the sieve layer to form an integrated structure, and the size gradient of the channel structure contained in the integrated polybenzimidazole gradient film decreases from the polybenzimidazole support layer to the polybenzimidazole sieve layer along the thickness direction.

[0062] In some embodiments, the ion channel size of the polybenzimidazole support layer is in the angstrom to nanometer range.

[0063] In some embodiments, the thickness of the polybenzimidazole support layer is 20~100µm.

[0064] In some embodiments, the present invention constructs a highly selective polybenzimidazole sieving thin layer along the thickness direction of the membrane, with hydrophilic narrow ion channels at the angstrom level, ensuring precise ion sieving. The thickness of the polybenzimidazole sieving layer can be adjusted from 0.1 to 10 µm, and its microstructure is a dense structure with narrow and interconnected angstrom-level channels.

[0065] In some embodiments, the total thickness of the integrated polybenzimidazole gradient film is 20~110µm.

[0066] Furthermore, the gradient of the integrated polybenzimidazole gradient membrane of the present invention refers to the following: the polybenzimidazole sieve layer is a narrow and interconnected angstrom-level channel, the polybenzimidazole support layer is a wide and interconnected pore channel, and there is a change in channel structure along the thickness direction of the integrated polybenzimidazole gradient membrane, that is, from the polybenzimidazole support layer to the polybenzimidazole sieve layer, there are two types of ion channel structures.

[0067] As another aspect of the technical solution of the present invention, it also relates to the application of the integrated polybenzimidazole gradient membrane, which can be used in the fields of flow batteries, fuel cells, and water electrolysis for hydrogen production.

[0068] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention, and do not constitute any limitation thereof. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0069] The polybenzimidazole used in Examples 1-8 below was commercially available and purchased from Shanghai Shengjun Plastics Technology Co., Ltd., with the product model SJ-PBI.

[0070] Of course, in addition to using commercially available polybenzimidazole, homemade polybenzimidazole can also be used. The preparation method is as follows: Weigh 5g of P2O5 into a 100mL three-necked flask, then add 35mL of methanesulfonic acid, and then place it in a heating module, set the temperature to 80℃, and provide N2 atmosphere and mechanical stirring (130 r / min). After stirring for 30 min until fully dissolved, wait until the reaction system is clear and transparent to prove that the oxygen removal and dissolution are complete, then add 5.8 mmol of phenyltetramine monomer and 5.8 mmol of phenyl dicarboxylic acid monomer and raise the temperature to 100℃ for prepolymerization for 1h. Then raise the reaction temperature to 140℃ for polymerization for 1.5h-4h. After polymerization, precipitate in water, wash with alkali, wash with water until neutral, and dry to obtain polybenzimidazole.

[0071] The flow battery structures in Examples 1-8 below are as follows: The effective area is 3×3 cm. 2 The performance of the assembled flow battery was tested by sandwiching an integrated polybenzimidazole gradient membrane between a carbon felt electrode and a graphite plate, using two separate circulation pumps to deliver 45 mL of 1.7 MV fluid. 3.5+ / 3 M H2SO4 solution, using a LANHE battery tester (CT2001A, 5 V / 3 A, Wuhan Landian Electronics Co., Ltd.) at 40-200 mA cm⁻¹ -2 The flow battery was subjected to charge-discharge tests at 160 mA cm⁻¹ to evaluate its electrochemical performance. The cutoff voltage during the charge-discharge process ranged from 1 V to 1.55 V. -2 The charge-discharge cycle performance was tested with a cutoff voltage set from 1 V to 1.55 V to minimize corrosion of the carbon felt electrode and graphite plate. During the charge-discharge cycle test, when the discharge capacity decreased to below 30% of the initial value, the electrolyte was replaced and the test continued.

[0072] The fuel cell structure in Example 1 below is as follows: The performance of the integrated polybenzimidazole gradient membrane fuel cell was tested using an 890e Multi Range fuel cell test bench (Shanghai Qunyi). 1.5 g of polybenzimidazole was weighed and dissolved in 30 mL of dimethyl sulfoxide, heated to dissolve, and then centrifuged to obtain a polybenzimidazole solution. A commercial Pt / Ru / C (40% w / w / w Pt component) was used as the anode catalyst, and a commercial Pt / C (40% w / w Pt component) was used as the cathode catalyst. 10 mg of each catalyst powder was dispersed in 3 mL of a water / isopropanol mixed solution (V... 水 V 异丙醇The ratio of the catalyst solution to the cathode solution was 1:9. After ultrasonic treatment for 30 min, the above-mentioned polybenzimidazole solution was added, and ultrasonication was repeated for 30 min to obtain uniformly mixed anolyte catalyst solutions and cathode catalyst solutions. Subsequently, the anolyte catalyst solutions and cathode catalyst solutions were sprayed onto both sides of the integrated polybenzimidazole gradient membrane at 70°C (effective area 5 cm²). 2 In this integrated polybenzimidazole gradient membrane, the loading of both the cathode and anode catalysts on both sides is 0.6 mg / cm³. -2 An integrated polybenzimidazole gradient membrane supporting both anode and cathode catalysts was placed between two sheets of carbon paper (AVCARB GDS3250) to form a membrane electrode assembly. The prepared membrane electrode assembly was assembled onto an 890e Multi Range fuel cell test bench (Shanghai Qunyi), and fuel cell performance was measured at 80°C with an H2 / O2 (100% humidity) flow rate of 0.2 L / min and a back pressure of 0.1 MPa.

[0073] The structure of the water electrolysis battery in Example 1 is as follows:

[0074] Fabrication of the membrane electrode assembly: First, the carbon paper and nickel foam used as the gas diffusion layer were pretreated. The anode and cathode were carbon paper (Avcarb P75, 232 µm thick) and nickel foam (0.6 mm thick), respectively. The nickel foam was cut into 2.25 cm × 2.25 cm pieces, washed with acetone and ethanol to remove surface impurities and oxide layers, and dried in a 60°C oven for 12 h. The carbon paper required no treatment and was simply cut to the same size as the nickel foam. The integrated polybenzimidazole gradient membrane was soaked in 1 M KOH solution for 24 hours, and then the alkaline solution was removed from the surface with pure water. 1.5 g of polybenzimidazole was weighed and dissolved in 30 mL of dimethyl sulfoxide, heated to dissolve, and then centrifuged to obtain the polybenzimidazole solution. Pt / C and IrO2 were used as the cathode and anode catalysts, respectively. 10 mg of each catalyst powder was dispersed in 3 mL of a water / isopropanol mixed solution (V... 水 V 异丙醇 The ratio of the catalyst solution to the anode catalyst solution was 1:9. After ultrasonic treatment for 30 min, the above-mentioned polybenzimidazole solution was added, and ultrasonication was repeated for 30 min to obtain uniformly mixed cathode and anode catalyst solutions. Subsequently, the cathode and anode catalyst solutions were sprayed onto carbon paper and nickel foam (effective area 5 cm²) at 70 °C, respectively. 2 The loading amounts of the cathode catalyst on carbon paper and the anode catalyst on nickel foam were both 2 mg / cm³. -2After spraying, the coating is dried using residual heat on a film scraper. Finally, the integrated polybenzimidazole gradient membrane is placed between the carbon paper supporting the cathode catalyst layer and the nickel foam supporting the anode catalyst layer. The integrated polybenzimidazole gradient membrane is in contact with the cathode catalyst layer and the anode catalyst layer on both sides, forming a membrane electrode assembly. A flow field plate and a bipolar plate are then placed sequentially from the inside to the outside on both sides of the membrane electrode assembly, and the assembled assembly yields an electrolytic water battery for electrochemical testing.

[0075] Electrolysis performance testing: The water electrolysis device was used to evaluate the performance of the electrolytic cell. A multi-channel Ivium electrochemical workstation was used to control the battery voltage and current. During the test, the electrolyte solution, preheated to 50°C, was introduced into the anode side at a flow rate of 5 mL / min. The polarization curve (current density versus battery voltage curve) was measured, with a scanning voltage range of 1.3–2.5 V and a scanning rate of 5 mV / s. Before recording the first polarization curve, the battery was activated for a period of time under varying current. The test was conducted at 60°C and 600 mA / cm². 2 The stability of the battery was tested under a constant current density.

[0076] Example 1

[0077] (1) Polybenzimidazole was dissolved in N-methylpyrrolidone, and then diethylene glycol diethyl ether was added. The mass ratio of polybenzimidazole to diethylene glycol diethyl ether was 40:60, and the ratio of the total mass of diethylene glycol diethyl ether and polybenzimidazole to the volume of N-methylpyrrolidone was 14 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto polyethylene terephthalate (PET) substrate. The mixture was dried in an oven at 80°C for 8 hours to obtain a dense diethylene glycol diethyl ether solvated polybenzimidazole support layer.

[0078] (2) Polybenzimidazole is dissolved in N-methylpyrrolidone, wherein the mass ratio of polybenzimidazole to N-methylpyrrolidone is 15 g / mL, and then coated onto the dense diethylene glycol diethyl ether solvated polybenzimidazole support layer obtained in step (1), and dried in an oven at 90°C for 8 hours to obtain an integrated polybenzimidazole membrane.

[0079] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 2 mol / L hydrochloric acid solution at room temperature for 12 h, and then washed with water for 4 h to remove residual hydrochloric acid. The in-situ etching process and the etching agent removal process are repeated twice to obtain an integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 8 µm and the thickness of the polybenzimidazole support layer is about 40 µm.

[0080] The cross-sectional SEM image of the integrated polybenzimidazole gradient membrane obtained in this embodiment is shown below. Figure 1 As shown in (a), a magnified SEM image of the polybenzimidazole support layer is shown below. Figure 1 As shown in (b), the TEM image of the polybenzimidazole sieve layer is as follows. Figure 2 As shown.

[0081] The performance test of the flow battery obtained by the integrated polybenzimidazole gradient membrane in this embodiment is as follows: Figure 3 and Figure 4 As shown, where Figure 3 Cyclic data under different current densities, Figure 4 For long-term cycling data, the results show that at 160 mA cm⁻¹ -2 The lower flow battery exhibits a coulombic efficiency (CE) of 99.4%, a voltage efficiency (VE) of 86.0%, and an energy efficiency (EE) of 85.5%. This integrated polybenzimidazole gradient membrane was assembled into a fuel cell for testing at 80°C, achieving a maximum output power of 1.28 W / cm². 2 For performance testing, please refer to the following: Figure 5 and Figure 6 As shown, where Figure 5 The polarization curve is shown. Figure 6 This data represents a long-term lifespan test. The integrated polybenzimidazole gradient membrane was assembled into a water electrolysis battery for testing. At 80℃ and 2V, the current reached 1.9 A / cm². 2 For performance testing, please refer to the following: Figure 7 and Figure 8 As shown, where Figure 7 The polarization curve is shown. Figure 8 This is data from long-term lifespan testing.

[0082] Example 2

[0083] (1) Polybenzimidazole was dissolved in N-methylpyrrolidone, and then ferrous chloride was added. The mass ratio of polybenzimidazole to ferrous chloride was 70:30, and the ratio of the total mass of ferrous chloride and polybenzimidazole to the volume of N-methylpyrrolidone was 14 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a polyethylene terephthalate (PET) substrate. The mixture was dried in an oven at 80°C for 8 hours to obtain a dense ferrous chloride solvated polybenzimidazole support layer.

[0084] (2) Polybenzimidazole is dissolved in N-methylpyrrolidone, wherein the mass ratio of polybenzimidazole to N-methylpyrrolidone is 15 g / mL, and then coated onto the dense ferrous chloride solvated polybenzimidazole support layer obtained in step (1), and dried in an oven at 90°C for 6 h to obtain an integrated polybenzimidazole membrane.

[0085] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 2 mol / L hydrochloric acid solution at room temperature for 12 h, and then washed with water for 4 h to remove residual hydrochloric acid. The in-situ etching process and the etching agent removal process are repeated twice to obtain the integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 10 µm and the thickness of the polybenzimidazole support layer is about 60 µm.

[0086] The performance test of the flow battery obtained by the integrated polybenzimidazole gradient membrane in this embodiment is as follows: Figure 9 and Figure 10 As shown, where Figure 9 Cyclic data under different current densities, Figure 10 For lifetime test data, the results show that at 160 mA cm⁻¹ -2 The lower flow battery has a coulombic efficiency (CE) of 99.6%, a voltage efficiency (VE) of 82.6%, and an energy efficiency (EE) of 82.2%.

[0087] Example 3

[0088] (1) Polybenzimidazole was dissolved in N,N-dimethylformamide, and then chromium chloride was added. The mass ratio of polybenzimidazole to chromium chloride was 70:30, and the ratio of the total mass of chromium chloride and polybenzimidazole to the volume of N,N-dimethylformamide was 15 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a polyethylene terephthalate (PET) substrate. The substrate was dried in an oven at 60°C for 24 h to obtain a dense chromium chloride solvated polybenzimidazole support layer.

[0089] (2) Polybenzimidazole is dissolved in N-methylpyrrolidone, wherein the mass ratio of polybenzimidazole to N-methylpyrrolidone is 25 g / mL, and then coated onto the dense chromium chloride solvated polybenzimidazole support layer obtained in step (1), and dried in an oven at 80°C for 6 h to obtain an integrated polybenzimidazole membrane.

[0090] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 1 mol / L hydrochloric acid solution at room temperature for 12 h, and then washed with water for 5 h to remove residual hydrochloric acid. The in-situ etching process and the etching agent removal process are repeated 3 times to obtain the integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 8 µm and the thickness of the polybenzimidazole support layer is about 35 µm.

[0091] The integrated polybenzimidazole gradient membrane obtained in this embodiment operates at 160 mA cm⁻¹. -2 The lower flow battery has a coulombic efficiency of 99.3%, a voltage efficiency of 85.2%, and an energy efficiency of 84.4%.

[0092] Example 4

[0093] (1) Polybenzimidazole was dissolved in N-methylpyrrolidone, and then polyethylene glycol was added. The mass ratio of polybenzimidazole to polyethylene glycol was 70:30, and the ratio of the total mass of polyethylene glycol and polybenzimidazole to the volume of N-methylpyrrolidone was 10 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a PET substrate. The substrate was dried in an oven at 60°C for 24 h to obtain a dense polyethylene glycol solvated polybenzimidazole support layer.

[0094] (2) Polybenzimidazole is dissolved in dimethyl sulfoxide, wherein the mass ratio of polybenzimidazole to the volume ratio of dimethyl sulfoxide is 30 g / mL, and then coated onto the dense polyethylene glycol solvated polybenzimidazole support layer obtained in step (1), and dried in an oven at 80°C for 6 h to obtain an integrated polybenzimidazole membrane.

[0095] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in a 1 mol / L phosphoric acid aqueous solution at 26°C for 24 h, and then washed with water for 5 h to remove residual phosphoric acid. The in-situ etching process and the etching agent removal process are repeated 4 times to obtain an integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 3 µm and the thickness of the polybenzimidazole support layer is about 36 µm.

[0096] The integrated polybenzimidazole gradient membrane obtained in this embodiment operates at 160 mA cm⁻¹. -2 The lower flow battery has a coulombic efficiency of 99.1%, a voltage efficiency of 85.3%, and an energy efficiency of 84.6%.

[0097] Example 5

[0098] (1) Polybenzimidazole was dissolved in methanesulfonic acid, and then polyethyleneimine was added. The mass ratio of polybenzimidazole to polyethyleneimine was 60:40, and the ratio of the total mass of polyethyleneimine and polybenzimidazole to the volume of methanesulfonic acid was 20 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a PET substrate. The mixture was dried in an oven at 80°C for 24 h to obtain a dense polyethyleneimine-solventized polybenzimidazole support layer.

[0099] (2) Polybenzimidazole is dissolved in dimethyl sulfoxide, wherein the mass ratio of polybenzimidazole to the volume ratio of dimethyl sulfoxide is 10 g / mL, and then coated onto the dense polyethyleneimine solvated polybenzimidazole support layer obtained in step (1), and dried in an oven at 80°C for 6 h to obtain an integrated polybenzimidazole membrane.

[0100] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 1 mol / L sulfuric acid solution at 40°C for 6 h, and then washed with water for 12 h to remove residual sulfuric acid. The in-situ etching process and the etching agent removal process are repeated twice to obtain an integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 7 µm and the thickness of the polybenzimidazole support layer is about 50 µm.

[0101] The integrated polybenzimidazole gradient membrane obtained in this embodiment operates at 160 mA cm⁻¹. -2 The lower flow battery has a coulombic efficiency of 99.3%, a voltage efficiency of 84.6%, and an energy efficiency of 84.0%.

[0102] Example 6

[0103] (1) Polybenzimidazole was dissolved in N-methylpyrrolidone, and then 18-crown ether-6 was added. The mass ratio of polybenzimidazole to 18-crown ether-6 was 70:30, and the ratio of the total mass of 18-crown ether-6 and polybenzimidazole to the volume of N-methylpyrrolidone was 60 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a PET substrate. The mixture was dried in an oven at 90°C for 24 h to obtain a dense 18-crown ether-6 solvated polybenzimidazole support layer.

[0104] (2) Polybenzimidazole is dissolved in methanesulfonic acid, wherein the mass ratio of polybenzimidazole to the volume of methanesulfonic acid is 25 g / mL. Then, it is coated onto the dense 18-crown ether-6 solvated polybenzimidazole support layer obtained in step (1) and dried in an oven at 80°C for 6 h to obtain an integrated polybenzimidazole membrane.

[0105] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 1 mol / L potassium hydroxide solution at 50°C for 24 h, and then washed with water for 12 h to remove residual potassium hydroxide. The in-situ etching process and etching agent removal process are repeated 4 times to obtain an integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 8 µm and the thickness of the polybenzimidazole support layer is about 55 µm.

[0106] The integrated polybenzimidazole gradient membrane obtained in this embodiment operates at 160 mA cm⁻¹. -2 The lower flow battery has a coulombic efficiency of 99.3%, a voltage efficiency of 84.1%, and an energy efficiency of 83.5%.

[0107] Example 7

[0108] (1) Polybenzimidazole was dissolved in dimethyl sulfoxide, and then benzo-15-crown ether-5 was added. The mass ratio of polybenzimidazole to benzo-15-crown ether-5 was 30:70, and the ratio of the total mass of benzo-15-crown ether-5 and polybenzimidazole to the volume of dimethyl sulfoxide was 20 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a PET substrate. The mixture was dried in an oven at 90°C for 24 h to obtain a dense benzo-15-crown ether-5 solvated polybenzimidazole support layer.

[0109] (2) Polybenzimidazole is dissolved in methanesulfonic acid, wherein the mass ratio of polybenzimidazole to the volume of methanesulfonic acid is 12 g / mL. Then, it is coated onto the dense benzo-15-crown-5 solvated polybenzimidazole support layer obtained in step (1) and dried in an oven at 90°C for 6 hours to obtain an integrated polybenzimidazole membrane.

[0110] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 1 mol / L sodium hydroxide solution at 100°C for 18 h, and then washed with water for 4 h to remove residual sodium hydroxide. The in-situ etching process and etching agent removal process are repeated twice to obtain an integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 8 µm and the thickness of the polybenzimidazole support layer is about 55 µm.

[0111] The integrated polybenzimidazole gradient membrane obtained in this embodiment operates at 160 mA cm⁻¹. -2 The lower flow battery has a coulombic efficiency of 99.0%, a voltage efficiency of 84.4%, and an energy efficiency of 83.6%.

[0112] Example 8

[0113] (1) Polybenzimidazole was dissolved in N,N-dimethylacetamide, and then dibenzo-18-crown ether-6 was added. The mass ratio of polybenzimidazole to dibenzo-18-crown ether-6 was 20:80, and the ratio of the total mass of dibenzo-18-crown ether-6 and polybenzimidazole to the volume of N,N-dimethylacetamide was 1 g / mL. The mixture was stirred vigorously to make it uniformly mixed, and then coated onto a PET substrate. The mixture was dried in an oven at 40°C for 48 h to obtain a dense dibenzo-18-crown ether-6 solvated polybenzimidazole support layer.

[0114] (2) Polybenzimidazole is dissolved in methanesulfonic acid, wherein the mass ratio of polybenzimidazole to the volume of methanesulfonic acid is 1 g / mL. Then, it is coated onto the dense dibenzo-18-crown-6 solvated polybenzimidazole support layer obtained in step (1) and dried in an oven at 120°C for 1 h to obtain an integrated polybenzimidazole membrane.

[0115] (3) The integrated polybenzimidazole membrane obtained in step (2) is immersed in 1 mol / L sodium chloride solution at 80°C for 18 h, and then washed with water for 4 h to remove residual sodium chloride. The in-situ etching process and etching agent removal process are repeated twice to obtain the integrated polybenzimidazole gradient membrane, wherein the thickness of the polybenzimidazole sieve layer is about 10 µm and the thickness of the polybenzimidazole support layer is about 55 µm.

[0116] The integrated polybenzimidazole gradient membrane obtained in this embodiment operates at 160 mA cm⁻¹. -2 The lower flow battery has a coulombic efficiency of 99.0%, a voltage efficiency of 85.2%, and an energy efficiency of 84.3%.

[0117] Comparative Example 1

[0118] The difference between this comparative example and Example 1 is that in step (2), the mass ratio of polybenzimidazole to N-methylpyrrolidone is 0.8 g / mL, and the thickness of the polybenzimidazole sieve thin layer is controlled at 0.09 µm. The resulting thin layer is prone to defects, resulting in the coulombic efficiency of the battery assembled with the gradient membrane being less than 97%, which is not conducive to industrial production; or, when the mass ratio of polybenzimidazole to N-methylpyrrolidone is 35 g / mL, and the thickness of the thin layer exceeds 12 µm, the mass transfer resistance of the resulting thin layer is too large, resulting in the voltage efficiency of the battery assembled with the gradient membrane being less than 77%, which is difficult to meet the battery requirements.

[0119] Comparative Example 2

[0120] The difference between this comparative example and Example 1 is that: in step (1), the mass percentage of the small molecule sacrificial template in the polybenzimidazole support layer is 98%, and the resulting support layer is broken and difficult to form a film; if the mass percentage of the small molecule sacrificial template is 0.6%, the ion channel connectivity is low and the mass transfer resistance is large, resulting in a battery voltage efficiency of 60% for the obtained gradient film assembly.

[0121] Comparative Example 3

[0122] The difference between this comparative example and Example 1 is that step (2) was not performed, but step (3) was performed directly, that is, the dense diethylene glycol diethyl ether solvated polybenzimidazole support layer obtained in step (1) was immersed in 2 mol / L hydrochloric acid solution at room temperature for 12 h for in-situ etching.

[0123] The polybenzimidazole membrane obtained in this comparative example was assembled into a flow battery at 160 mA cm⁻¹. -2 The lower flow battery exhibits a coulombic efficiency of 96.9%, a voltage efficiency of 84.9%, and an energy efficiency of 82.2%, but excessive water migration is observed. The polybenzimidazole membrane was assembled into a fuel cell for testing; at 80°C, the maximum output power was 0.4 W / cm².2 After a period of operation, the battery is prone to short circuits. The polybenzimidazole membrane was assembled into a water electrolysis battery for testing; at 80℃ and 2V, the current reached 0.6A / cm. 2 After running for a period of time, the battery is prone to short circuit problems.

[0124] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for producing an integrated polybenzimidazole gradient membrane, characterized by, The application relates to a preparation method of an integrated polybenzimidazole gradient membrane. A first solution containing polybenzimidazole, a polar solvent and a small-molecule sacrificial template with organic solvent solubility is applied to the surface of a substrate, the polar solvent is removed by heating to form a dense small-molecule solvated polymer support layer, in the first solution, the mass percentage of the small-molecule sacrificial template in the sum of the mass of the polybenzimidazole is 30-80% based on 100%; A second solution containing polybenzimidazole and a polar solvent is applied to the surface of the small-molecule solvated polymer support layer, the polar solvent is removed by heating, and a screening layer is formed on the surface of the small-molecule solvated polymer support layer, wherein at least part of the polybenzimidazole on the side of the small-molecule solvated polymer support layer in contact with the screening layer is integrated with the polybenzimidazole in the screening layer to form an integrated structure, thus obtaining an integrated polybenzimidazole membrane, and the ratio of the mass of the polybenzimidazole to the volume of the polar solvent in the second solution is 1-30 g / mL; The integrated polybenzimidazole membrane is subjected to in-situ etching treatment with an etchant, so that the small-molecule sacrificial template in the small-molecule solvated polymer support layer is removed, and an integrated polybenzimidazole gradient membrane is obtained.

2. The method of claim 1, wherein: The small-molecule sacrificial template comprises a combination of one or more of ferrous chloride, ferric chloride, chromium chloride, zinc chloride, polyethylene glycol, polyethylene imine, 15-crown-5, 18-crown-6, benzo-15-crown-5, diphenyl-18-crown-6 and diethylene glycol diethyl ether; And / or, the polar solvent comprises a combination of one or more of N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone and methyl sulfonic acid.

3. The method of claim 1, wherein: In the first solution, the ratio of the sum of the mass of the small-molecule sacrificial template and the polybenzimidazole to the volume of the polar solvent is 1-95 g / mL; And / or, the preparation method comprises the following steps: firstly, dissolving the polybenzimidazole in the polar solvent to form a polymer solution, and then adding the small-molecule sacrificial template into the polymer solution and mixing thoroughly by ultrasonic or stirring to obtain the first solution.

4. The method of claim 2, wherein: In the first solution, the ratio of the sum of the mass of the small-molecule sacrificial template and the polybenzimidazole to the volume of the polar solvent is 10-60 g / mL; And / or, in the second solution, the ratio of the mass of the polybenzimidazole to the volume of the polar solvent is 10-25 g / mL; And / or, the preparation method comprises the following step: dissolving the polybenzimidazole in the polar solvent and mixing thoroughly by ultrasonic or stirring to obtain the second solution; And / or, the method for removing the polar solvent by heating comprises drying at 40-120 DEG C for 1-48 h; And / or, the preparation method comprises the following step: applying the first solution to the surface of the substrate by at least a casting method or a blade coating method; And / or, the preparation method comprises the following step: applying the second solution to the surface of the small-molecule solvated polymer support layer by at least a casting method or a blade coating method.

5. The method of claim 1, wherein: The etchant comprises at least one of dilute hydrochloric acid, dilute sulfuric acid, aqueous phosphoric acid, aqueous lithium hydroxide, aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous lithium chloride, aqueous sodium chloride, aqueous potassium chloride, aqueous ammonium chloride, and water; The preparation method further comprises: after the in-situ etching treatment is completed, eluting the etchant remaining on the surface of the prepared integrated polybenzimidazole gradient membrane with water, and the elution time is more than 1 hour. The in-situ etching treatment and the step of eluting the etchant are repeated more than 2 times. The integrated polybenzimidazole gradient membrane comprises:

6. The integrated polybenzimidazole gradient membrane produced by the method of any one of claims 1-5, characterized by, The polybenzimidazole support layer has wide and connected ion channels; The dense polybenzimidazole screening layer arranged on the surface of the polybenzimidazole support layer has narrow and connected Angstrom-level channels; The at least part of the polybenzimidazole on the side of the polybenzimidazole support layer in contact with the screening layer is integrally formed with the polybenzimidazole in the screening layer, the size of the channel structure contained in the polybenzimidazole support layer and the polybenzimidazole screening layer decreases in the thickness direction of the integrated polybenzimidazole gradient membrane, the ion channel size of the polybenzimidazole support layer is Angstrom-level to nanometer-level, and the thickness of the polybenzimidazole screening layer is 0.1-10 µm. The thickness of the polybenzimidazole support layer is 20-100 µm.

7. The integrated polybenzimidazole gradient membrane of claim 6, wherein: The total thickness of the integrated polybenzimidazole gradient membrane is 20-110 µm.

8. The integrated polybenzimidazole gradient membrane of claim 6, wherein:

9. The integrated polybenzimidazole gradient membrane prepared by the preparation method in any one of claims 1-5 is applied in a renewable energy conversion device. The application comprises: the application of the integrated polybenzimidazole gradient membrane in the fields of fuel cells, flow batteries, or hydrogen production by water electrolysis.

10. Use according to claim 9, characterized in that, ​

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