High-performance alkaline water electrolysis composite diaphragm as well as preparation method and application thereof

Abstract

The invention relates to the technical field of hydrogen production through alkaline water electrolysis, in particular to a high-performance alkaline water electrolysis composite diaphragm as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, soaking an organic polymer matrix in a swelling solvent to obtain a swelled organic polymer matrix; s2, a swelling solvent is taken to be mixed with the precursor aqueous solution, and functional inorganic matter mother liquor is obtained; and S3, adding the swelled organic polymer matrix in the step S1 into the functional inorganic matter mother liquor in the step S2, standing, carrying out in-situ growth reaction, washing and drying to obtain an organic-inorganic composite diaphragm, namely the high-performance alkaline water electrolysis composite diaphragm. Compared with the prior art, the firmness of the composite diaphragm can be effectively enhanced, the hydrophilicity of the composite diaphragm is improved, the surface resistance of the composite diaphragm is reduced, and the electrolytic performance and the electrolytic stability of the composite diaphragm are enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of alkaline water electrolysis hydrogen production, and in particular to a high-performance alkaline water electrolysis composite diaphragm and a preparation method and application thereof. Background Art

[0002] Hydrogen energy is considered the "ultimate energy" of the 21st century due to its high calorific value, diverse sources, abundant reserves, and suitability for large-capacity, long-term storage. It has become an important component of the future national energy system and an important carrier for energy-consuming terminals to achieve green and low-carbon transformation. As a "zero-carbon emission" renewable energy, hydrogen energy can achieve efficient conversion between hydrogen energy and electrical energy through water electrolysis technology, while overcoming the discontinuity and instability of wind and solar power generation, and realizing large-scale energy conversion and storage. Therefore, conducting research on renewable energy water electrolysis hydrogen production technology meets the country's major strategic needs and is of great significance to the sustainable development of human society.

[0003] Compared with technologies such as proton exchange membrane electrolysis for hydrogen production, alkaline water electrolysis for hydrogen production has the advantages of mature technology and low cost. It has been commercialized and is the mainstream technology for the industrialization of electrolytic hydrogen production. The diaphragm material is the core component and key material of the water electrolysis hydrogen production device, which directly affects the energy consumption, gas purity, electrolysis stability and safety of water electrolysis. Polymer diaphragms are widely used in alkaline electrolysis for hydrogen production because of their high chemical stability and mechanical strength. However, due to the low surface energy of this type of membrane, the aqueous electrolyte cannot evenly infiltrate the membrane pores, and the transfer of hydroxide ions is hindered, resulting in an increase in the internal resistance of the electrolysis system and an increase in the energy consumption of electrolysis. To this end, it is necessary to hydrophilize the polymer to enhance the hydrophilicity and reduce the surface resistance.

[0004] Commonly used hydrophilic improvements are divided into two categories. One is to graft hydrophilic functional groups on the polymer surface, such as sulfonation treatment (Chinese patents CN119082984A, CN118292259A, etc.). However, the hydrophilic functional groups are prone to instability and detachment in the high-temperature, strongly alkaline electrolysis of water to produce hydrogen. The hydrophilicity of the modified film is difficult to maintain, and the membrane surface resistance increases again after a period of operation, which ultimately affects the electrolysis efficiency. The other is to add inorganic substances to the polymer casting solution, and blend the polymer with the inorganic powder to prepare a composite membrane. Hydrophilic inorganic substances can effectively reduce membrane resistance, thereby reducing electrolysis energy consumption. A typical example is Composite diaphragms, similar methods include Chinese patents CN114207189A, CN115029732A, CN115677269A, etc. The common problem of this type of composite diaphragm is that the surface of the diaphragm is prone to cracking and the inorganic matter is prone to powdering. The essential reason is that the inorganic matter has poor compatibility with the organic polymer matrix, resulting in a weak organic-inorganic bond and self-agglomeration of the inorganic matter. In addition, in order for the composite diaphragm to obtain better hydrophilicity and mechanical strength, the particle size of the inorganic matter must reach the micron or even nanometer level, and the smaller the particle, the more serious the agglomeration phenomenon, which puts higher requirements on the dispersion process of the material and is not conducive to the scale-up production of the composite diaphragm. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art that the interface compatibility between organic and inorganic substances in the organic-inorganic composite membrane is poor, which leads to the easy agglomeration and shedding of inorganic substances in the polymer matrix, and to provide a high-performance alkaline water electrolysis composite membrane and its preparation method and application, which can effectively enhance the firmness of the composite membrane, improve the hydrophilicity of the composite membrane, reduce the surface resistance of the composite membrane, and enhance the electrolytic performance and electrolytic stability of the composite membrane.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing a high-performance alkaline water electrolysis composite diaphragm, comprising the following steps:

[0008] S1, soaking the organic polymer matrix in a swelling solvent to obtain a swollen organic polymer matrix;

[0009] S2, taking another swelling solvent and mixing it with the precursor aqueous solution to obtain a functional inorganic mother solution;

[0010] S3, adding the organic polymer matrix swollen in step S1 to the functional inorganic mother solution in step S2 and letting it stand, in-situ growth reaction, washing and drying to obtain an organic-inorganic composite membrane, i.e., a high-performance alkaline water electrolysis composite membrane, and completing.

[0011] Further, in step S1, the organic polymer matrix includes but is not limited to polyphenylene sulfide (PPS), polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polyimide (PI), and its existing forms include porous membrane, fiber membrane, non-woven fabric, woven fabric, composite fabric;

[0012] In steps S1 and S2, the swelling solvent includes but is not limited to N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and toluene;

[0013] The volume ratio of the organic polymer matrix to the swelling solvent is 1:20-200.

[0014] Furthermore, in step S1, since different organic polymer matrices have different swelling difficulties, in order to make the organic polymer matrix reach a certain swelling degree without dissolving, the soaking time is generally 1 to 10 days.

[0015] Furthermore, in step S1, in order to accelerate the infiltration process, the organic polymer matrix is ​​heat-treated at 25-100°C.

[0016] Furthermore, in step S2, the precursor aqueous solution is a mixed solution containing divalent metal cations, trivalent metal cations, and alkaline substances.

[0017] Furthermore, the divalent metal cations include but are not limited to Mg 2+ 、Zn 2+ 、Co 2+ 、Ni 2+ , Fe 2+ ...etc.; trivalent metal cations include but are not limited to Al 3+ , Fe 3+ One or more of; alkaline substances include but are not limited to sodium hydroxide, potassium hydroxide, urea, ammonia water, hexamethylenetetramine;

[0018] The concentration of the divalent metal cation is 0.02-1 mol / L, the concentration of the trivalent metal cation is 0.02-1 mol / L, and the concentration of the alkaline substance is 0.1-5 mol / L.

[0019] Furthermore, in step S2, the volume ratio of the swelling solvent to the precursor aqueous solution is 1:0.3-3.

[0020] Furthermore, in step S2, the functional inorganic mother solution is hydrophilic.

[0021] Furthermore, in step S3, the volume ratio of the swollen organic polymer matrix to the functional inorganic substance mother solution is 1:1 to 50;

[0022] The in-situ growth reaction includes but is not limited to a co-precipitation method and a hot solvent method, wherein the free volume or surface micropores in the organic polymer matrix are used as nucleation sites, and a suitable reaction environment is applied to allow the functional inorganic substance to grow outward from the inside of the organic polymer matrix.

[0023] Furthermore, in step S3, the swollen organic polymer matrix is ​​added to the functional inorganic substance mother solution and allowed to stand for 0.5 to 5 hours, so that the precursor solution is fully introduced into the organic polymer matrix.

[0024] Furthermore, in step S3, washing is performed by alternately washing with deionized water and ethanol, the drying temperature is 50 to 80° C., and the drying time is 6 to 24 hours.

[0025] Furthermore, when the swelling solvent is immiscible with the precursor aqueous solution, the preparation method comprises the following steps:

[0026] S1, soaking the organic polymer matrix in a swelling solvent to obtain a swollen organic polymer matrix, placing the organic polymer matrix in a medium solvent to replace the swelling solvent with the medium solvent, and obtaining a replaced organic polymer matrix;

[0027] S2, taking another medium solvent and a precursor aqueous solution and mixing them to obtain a functional inorganic mother solution;

[0028] S3, adding the organic polymer matrix replaced in step S1 to the functional inorganic mother solution in step S2 and letting it stand, in-situ growth reaction, washing and drying to obtain an organic-inorganic composite diaphragm, i.e., a high-performance alkaline water electrolysis composite diaphragm, and completing.

[0029] Furthermore, the medium solvent is a solvent that is miscible with both the precursor aqueous solution and the swelling solvent, including but not limited to ethanol, acetone, and tetrahydrofuran;

[0030] In step S1, the volume ratio of the swollen organic polymer matrix to the medium solvent is 1:50-200;

[0031] In step S2, the volume ratio of the precursor aqueous solution to the medium solvent is 1:0.3-3;

[0032] In step S3, the volume ratio of the replaced organic polymer matrix to the functional inorganic substance mother liquid is 1:1-50.

[0033] Furthermore, the swollen organic polymer matrix is ​​placed in a medium solvent, ultrasonicated for 0.5 to 2 hours, and then a new medium solvent is replaced, and ultrasonicated for 3 to 5 times to allow the medium solvent to fully fill the organic polymer matrix.

[0034] The second technical solution of the present invention is to provide a high-performance alkaline water electrolysis composite diaphragm, characterized in that it is prepared by the preparation method.

[0035] Furthermore, the composite membrane includes an organic polymer matrix and a functional inorganic substance grown in situ on the surface and inside of the organic polymer matrix, the functional inorganic substance completely covers the surface of the organic polymer matrix, and the functional inorganic substance presents a two-dimensional lamellar / porous structure and is inserted into the interior of the organic polymer matrix.

[0036] Furthermore, unlike the common organic-inorganic composite membrane structure, the grown functional inorganic material can completely cover the surface of the organic polymer matrix, so it can be completely wetted by water, thus showing super-hydrophilicity. The functional inorganic material presents an ordered and two-dimensional sheet / porous structure, and is inserted into the interior of the organic polymer matrix, which is conducive to the absorption of alkaline electrolyte, promoting the conduction of hydroxide ions and improving the firmness of the organic-inorganic bond. Moreover, the grown functional inorganic material has intrinsic hydroxide ion conduction ability, which can further reduce the membrane surface resistance, thereby reducing the electrolysis energy consumption.

[0037] Furthermore, the functional inorganic substances include but are not limited to covalent organic frameworks, perovskite oxides, and layered hydroxides having the ability to transport hydroxide ions.

[0038] Furthermore, the functional inorganic substances include but are not limited to modified covalent organic frameworks, modified perovskite oxides, and layered hydroxides.

[0039] Furthermore, the modified covalent organic framework includes a modified covalent organic framework incorporating zirconate;

[0040] The modified perovskite oxide includes a modified perovskite oxide doped with a cationic imidazole group, a quaternary ammonium group, a polybenzimidazolium or a viologen;

[0041] The layered hydroxide includes but is not limited to Mg(OH) 2 、Co(OH) 2 , MgAl LDH, ZnAl LDH, CoAlLDH, NiFe LDH, ZnMgAl LTTH, FeCuNi LTTH.

[0042] The third technical solution of the present invention is to provide a high-performance alkaline water electrolysis composite diaphragm for use in the field of alkaline water electrolysis hydrogen production.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] (1) The composite membrane prepared by the present invention has low surface resistance and good stability. The functional inorganic substance not only has good hydrophilicity, but also has intrinsic hydroxide ion conductivity. After the functional inorganic substance is introduced, the surface resistance of the composite membrane is significantly reduced, showing excellent electrolytic performance. In particular, the present invention regulates the swelling of the organic polymer matrix to induce the in-situ growth of the functional inorganic substance from the inside of the membrane. The functional inorganic substance is pinned inside the composite membrane, thereby enhancing the bonding strength between the functional inorganic substance and the organic polymer matrix, effectively preventing the functional inorganic substance from falling off, and improving the structural and performance stability of the composite membrane.

[0045] (2) The functional inorganic particles in the present invention are fine and evenly dispersed, the composite membrane has good hydrophilic stability, and the air tightness is enhanced. The present invention creates dense nucleation sites for the functional inorganics by regulating the swelling of the organic polymer matrix. Under the limited organic polymer matrix growth environment, the generated functional inorganics are fine and dispersed, which effectively prevents the aggregation of the functional inorganics, and the hydrophilicity and hydrophilic stability of the composite membrane are enhanced. In addition, the fine functional inorganics can fill the pores of the organic polymer matrix of the composite membrane, enhancing the air tightness of the composite membrane.

[0046] (3) The present invention achieves non-destructive regulation of the organic polymer matrix of the composite membrane, and the regulation process is gentle and effective, thereby improving the service life of the composite membrane. Compared with existing chemical modifications (such as sulfonation treatment), the present invention utilizes the swelling characteristics of the organic polymer matrix itself for reversible regulation, does not use highly corrosive solvents, does not destroy the organic polymer matrix of the composite membrane, and ensures the mechanical strength of the composite membrane. The close combination of the organic polymer matrix and the functional inorganic substance further improves the toughness of the composite membrane.

[0047] (4) The preparation method of the present invention is simple and easy to implement, safe to operate, and easy to industrialize. The composite diaphragm prepared by the present invention has excellent electrolytic performance and stability in hydrogen production by alkaline water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The process flow chart of the preparation method of the high-performance alkaline water electrolysis composite diaphragm of the present invention;

[0049] Figure 2 Characterization diagram of the composite diaphragm shown in Example 1: (a) surface morphology - 1 mm; (b) surface morphology - 200 nm; (c) cross-sectional morphology - 10 μm; (dg) cross-sectional energy spectrum diagram: (d) cross-sectional morphology, (e) Ni element distribution in the corresponding area, (f) Fe element distribution in the corresponding area, (g) O element distribution in the corresponding area;

[0050] Figure 3 The firmness test diagrams of the composite diaphragms prepared in Examples 1 to 5 and Comparative Examples 1 to 4 are as follows: (a) the swelling rate of the diaphragms prepared in each preparation process; (b) the mass loss rate of the diaphragm in high-frequency oscillation; (cf) the morphology of the composite diaphragms before and after the firmness test: (c) Comparative Example 2-before the test, (d) Example 1-before the test, (e) Comparative Example 2-after the test, (f) Example 1-after the test;

[0051] Figure 4 The surface resistance test results of the diaphragms prepared in Examples 1 to 4 and Comparative Examples 1 to 3 are shown;

[0052] Figure 5The linear voltammograms of the diaphragms prepared in Examples 1 to 4 and Comparative Examples 1 to 3;

[0053] Figure 6 The electrolytic stability result diagrams of the composite diaphragms prepared in Example 1 and Comparative Example 2 are as follows: (ab) morphology diagrams after immersion: (a) Example 1, (b) Comparative Example 2; (c) electrolytic performance of Example 1 and Comparative Example 2 before and after immersion; (d) constant current timing voltage curve of Example 1 under working conditions. DETAILED DESCRIPTION

[0054] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments. Based on the given embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0055] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art.

[0056] In the following examples and comparative examples, PPS fabrics were made of TORCON manufactured by Toray Industries, Inc. TM PPS fabric, purchased from; PTFE porous membrane The membrane is Merck Millipore Filter membrane, model number is FHUP04700.

[0057] Example 1

[0058] A method for preparing a high-performance alkaline water electrolysis composite diaphragm, such as Figure 1 As shown, the following steps are included:

[0059] S1. Place a circular PPS fabric with a diameter of 3 cm in 60 mL of N-methylpyrrolidone and heat at 80° C. for 180 h to obtain a swollen PPS fabric;

[0060] S2, preparing a precursor aqueous solution of 0.6 mol / L nickel nitrate, 0.2 mol / L ferrous chloride, and 2 mol / L urea as solute, and mixing it with the same volume of N-methylpyrrolidone to form a uniform functional inorganic mother solution (functional inorganic-NiFe LDH);

[0061] S3, the PPS fabric swollen in step S1 is placed in 20 mL of the functional inorganic mother solution prepared in step S2 and allowed to stand for 2 hours, and then subjected to hydrothermal treatment at 90° C. for 8 hours. The PPS fabric after hydrothermal growth is taken out, washed with deionized water and ethanol respectively, and dried at 60° C. for 8 hours to finally obtain an organic-inorganic composite membrane.

[0062] Example 2

[0063] A method for preparing a high-performance alkaline water electrolysis composite diaphragm, compared with Example 1, uses other swelling solvents (toluene) for swelling, such as Figure 1 As shown, the following steps are included:

[0064] S1. Place a circular PPS fabric with a diameter of 3 cm in 60 mL of toluene, heat it to 100°C under condensation reflux conditions, and maintain it for 100 hours to obtain a swollen PPS fabric. Place the swollen PPS fabric in 60 mL of ethanol, ultrasonically treat it for 1 hour, and then place the PPS fabric in 60 mL of fresh ethanol and continue ultrasonicating it. After repeating the ultrasonic treatment 3 times, the deionized water and the ultrasonically treated liquid are completely fused, that is, the toluene in the PPS is completely replaced by ethanol.

[0065] S2, preparing a precursor aqueous solution of 0.6 mol / L nickel nitrate, 0.2 mol / L ferrous chloride, and 2 mol / L urea as solute, and mixing it with the same volume of ethanol to form a uniform functional inorganic mother solution (functional inorganic-NiFe LDH);

[0066] S3, the PPS fabric fully filled with ethanol after swelling in step S1 is placed in 20 mL of the functional inorganic mother solution prepared in step S2 and allowed to stand for 2 hours, and then hydrothermally treated at 90°C for 8 hours. The PPS fabric after hydrothermal growth is taken out, washed with deionized water and ethanol respectively, and dried at 60°C for 8 hours to finally obtain an organic-inorganic composite membrane.

[0067] Example 3

[0068] A method for preparing a high-performance alkaline water electrolysis composite diaphragm, compared with Example 1, uses other functional inorganic mother liquids, such as Figure 1 As shown, the following steps are included:

[0069] S1. Place a circular PPS fabric with a diameter of 3 cm in 60 mL of N-methylpyrrolidone and heat at 80° C. for 180 h to obtain a swollen PPS fabric;

[0070] S2, preparing a precursor aqueous solution containing 0.4 mol / L aluminum nitrate, 0.2 mol / L magnesium chloride and 3 mol / L urea as solute, and mixing it with the same volume of N-methylpyrrolidone to form a uniform functional inorganic mother solution (functional inorganic-MgAlLDH);

[0071] S3, placing the pre-wetted PPS fabric in step S1 into 20 mL of the functional inorganic mother solution prepared in step S2 and allowing it to stand for 2 hours, and then hydrothermally treating it at 140° C. for 12 hours. Taking out the PPS fabric after the hydrothermal growth, washing it with deionized water and ethanol respectively, and drying it at 60° C. for 8 hours, finally obtaining an organic-inorganic composite membrane.

[0072] Example 4

[0073] A method for preparing a high-performance alkaline water electrolysis composite membrane, compared with Example 1, adopts another in-situ growth method (coprecipitation synthesis method), such as Figure 1 As shown, the following steps are included:

[0074] S1. Place a circular PPS fabric with a diameter of 3 cm in 60 mL of N-methylpyrrolidone and heat at 80° C. for 180 h to obtain a swollen PPS fabric;

[0075] S2. Prepare the following solutions respectively: 1) a precursor aqueous solution in which the solute is 0.06 mol / L nickel nitrate and 0.03 mol / L iron nitrate, which is mixed with the same volume of N-methylpyrrolidone (NMP) to form a uniform precursor NMP aqueous solution (solution ①); 2) a solute in which the solute is 0.5 mol / L sodium hydroxide aqueous solution, which is mixed with the same volume of NMP to form a uniform NMP aqueous solution (solution ②).

[0076] S3, put the swollen PPS fabric in step S1 into 60 mL of solution ① prepared in step S2 and let it stand for 1 hour, take out the PPS fabric and put it into 60 mL of solution ② prepared in step S2 and let it stand for 1 hour, and repeat the above steps 3 times. Take out the PPS fabric after the coprecipitation growth, wash it with deionized water and ethanol respectively, and dry it at 60°C for 8 hours to finally obtain an organic-inorganic composite membrane.

[0077] Example 5

[0078] A method for preparing a high-performance alkaline water electrolysis composite diaphragm, compared with Example 1, using other organic polymer matrix (PTFE porous membrane), such as Figure 1 As shown, the following steps are included:

[0079] S1. Place a circular PTFE porous membrane with a diameter of 3 cm in 60 mL of n-hexane and heat it at 60°C for 7 days to obtain a swollen PTFE porous membrane. Place the swollen PTFE porous membrane in 60 mL of ethanol and perform ultrasonic treatment for 1 h. Replace with 60 mL of fresh ethanol and repeat the ultrasonic treatment 3 times to obtain a PTFE porous membrane fully filled with ethanol after swelling.

[0080] S2, preparing a precursor aqueous solution of 0.6 mol / L nickel nitrate, 0.2 mol / L ferrous chloride, and 2 mol / L urea as solute, and mixing it with the same volume of ethanol to form a uniform functional inorganic mother solution (functional inorganic-NiFe LDH);

[0081] S3, the PTFE porous membrane fully filled with ethanol after swelling in step S1 is placed in 20 mL of the functional inorganic mother solution prepared in step S2 and allowed to stand for 2 hours, and then hydrothermally treated at 90° C. for 8 hours. The hydrothermally grown PTFE porous membrane is taken out, washed with deionized water and ethanol respectively, and dried at 60° C. for 8 hours to finally obtain an organic-inorganic composite membrane.

[0082] Comparative Example 1

[0083] A circular PPS fabric with a diameter of 3 cm was taken without any process treatment as the original film control.

[0084] Comparative Example 2

[0085] Compared with Example 1, most of the steps are the same, except that step S1 is omitted and the PPS fabric is not swollen.

[0086] Comparative Example 3

[0087] A method for preparing a water electrolysis composite diaphragm, compared with Example 1, uses a non-functional inorganic mother solution, and comprises the following steps:

[0088] S1. Place a circular PPS fabric with a diameter of 3 cm in 60 mL of N-methylpyrrolidone and heat at 80° C. for 180 h to obtain a swollen PPS fabric;

[0089] S2, 6.25mmol ZrOCl 2 8H 2 O was dissolved in 10 mL of deionized water and 9 mL of ethanol, placed on a constant temperature magnetic stirrer at 85 °C, stirred evenly, and 1 mL of ammonia water was added to form a uniform non-functional inorganic mother liquor (non-functional inorganic ZrO 2 );

[0090] S3, the PPS fabric swollen in step S1 is placed in 60 mL of ethanol, and after ultrasonic treatment for 1 hour, it is replaced with 60 mL of fresh ethanol, and the ultrasonic treatment is repeated 3 times. The PPS fabric after ultrasonic treatment is placed in 20 mL of non-functional inorganic mother liquor prepared in step S2 and allowed to stand for 5 hours, and then hydrothermally treated at 150°C for 24 hours. The PPS fabric after hydrothermal growth is taken out, washed with deionized water and ethanol respectively, and dried at 60°C for 8 hours to finally obtain an organic-inorganic composite membrane.

[0091] Comparative Example 4

[0092] A method for preparing a water electrolysis composite diaphragm, compared with Example 1, adopts a non-in-situ growth method (immersion coating), comprising the following steps:

[0093] S1. Place a circular PPS fabric with a diameter of 3 cm in 60 mL of N-methylpyrrolidone and heat at 80° C. for 180 h to obtain a swollen PPS fabric;

[0094] S2. Prepare an aqueous solution of 0.06 mol / L nickel nitrate, 0.03 mol / L iron nitrate, 0.2 mol / L formamide, and 0.5 mol / L sodium hydroxide, stir, centrifuge, and ball-mill to obtain NiFe LDH with a particle size of 200 nm. Take 6 g of NiFe LDH and add it to a solution consisting of 30 mL of ethanol and 30 mL of water, and mix and stir evenly.

[0095] S3. Immerse the swollen PPS fabric in 60 mL of the solution prepared in step S2, let it stand for 5 min, pull it up, immerse it again, let it stand, and pull it up. Then, take out the immersed PPS fabric, and dry it at 80° C. for 8 h to finally obtain an organic-inorganic composite membrane.

[0096] The composite membrane prepared in Example 1 was characterized. Figure 2 Characterization diagram of the composite diaphragm shown in Example 1, (a) surface morphology -1mm (microscope, macroscopic morphology), (b) surface morphology -200nm (SEM, microscopic morphology), (c) cross-sectional morphology -10μm, (dg) cross-sectional morphology and corresponding Ni, Fe, O element distribution diagram. Figure 2 It can be seen that the grown hydrophilic inorganic matter can completely cover the surface of the organic polymer matrix (2a) and evenly wrap the fiber filaments of the matrix (2c). The inorganic matter is in the form of two-dimensional sheets (2b) and is inserted into the interior of the polymer matrix (2d-g), reflecting the orderliness and firmness of the growth of the inorganic matter in the organic polymer matrix.

[0097] The firmness of the diaphragms prepared in Examples 1-5 and Comparative Examples 1-4 was tested. The diaphragms were subjected to 40KHz high-frequency oscillation for 60 minutes, and the mass of the diaphragms during this period was weighed. The mass loss rate of the diaphragms reflected the powder loss (inorganic matter shedding) situation. Figure 3 (a) lists the swelling ratios of the membranes during the preparation process. Figure 3(b) is the mass loss rate of the corresponding diaphragm when subjected to high-frequency ultrasonic vibration. As can be seen from the figure, the mass loss rate of the composite diaphragms prepared by Examples 1-5 and Comparative Example 3 is less than 10% when subjected to high-frequency ultrasonic vibration, and the mass loss mainly occurs in the first 20 minutes of ultrasonic vibration, and then gradually stabilizes. However, the mass loss rate of the composite diaphragms prepared by Comparative Examples 2 (non-swelling) and 4 (non-in-situ grown inorganic substances) exceeds 50% when subjected to high-frequency ultrasonic vibration. Further observation of the morphological changes of the composite diaphragms before and after the firmness test, Figure 3 (c) Comparative Example 2-before test, (d) Example 1-before test, (e) Comparative Example 2-after test, (f) Example 1-after test. It can be seen from the figure that the composite membrane prepared by Example 1 has no obvious surface change after being subjected to high-frequency ultrasonic vibration, while the composite membrane prepared by Comparative Example 2 has only a small amount of inorganic matter retained after being subjected to high-frequency ultrasonic vibration. This shows that the matrix swelling treatment and the in-situ growth of inorganic matter significantly improve the firmness of the composite membrane.

[0098] The surface resistance of the diaphragms prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was tested. According to the SJ / T10171.5-91 standard, the electrochemical impedance spectroscopy test method (frequency 0.1 Hz to 1 MHz) was used to test the impedance of the diaphragm at 80°C and 30 wt% KOH aqueous solution, and the surface resistance of the diaphragm was calculated ( Figure 4 The surface resistances of the composite diaphragms prepared in Examples 1 to 4 and Comparative Examples 2 to 3 were 0.1, 0.15, 0.12, 0.18, 0.24, and 0.3 Ω·cm, respectively. 2 The surface resistance of comparative example 1 (commercially available diaphragm) is 0.38Ω·cm 2 The resistance of the composite membranes prepared in Examples 1 to 4 and Comparative Examples 2 to 3 is lower than that of the commercially available membranes, and the resistance of the composite membranes prepared in Examples 1 to 4 is lower than that of the composite membranes prepared in Comparative Examples 2 to 3, among which the composite membrane prepared in Example 1 has the lowest surface resistance. This indicates that matrix swelling and the addition of functional inorganic substances can significantly reduce the surface resistance of the membrane.

[0099] The electrolytic performance of the diaphragms prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was tested by linear voltammetry. The test conditions were: nickel mesh as working electrode, 30 wt% KOH aqueous solution as electrolyte solution, electrolyte temperature of 80°C, and the test results are shown in Table 1. Figure 5. The electrolytic performance of each composite diaphragm and the original membrane is ranked from high to low as follows: Example 1> Example 2> Example 4> Example 3> Comparative Example 2> Comparative Example 3> Original membrane. The electrolytic performance of the composite diaphragm prepared by Example 1 after being grooved is outstanding. The voltage at a low current density of 500mA / cm2 is only 1.65V, and the highest current density of 2000mA / cm2 is achieved at a voltage not exceeding 2V, which is significantly better than the original membrane and the composite diaphragm that has not been subjected to swelling treatment and is directly compounded. It shows that the swelling treatment and the in-situ compounding of functional inorganic substances greatly enhance the electrolytic performance of the diaphragm.

[0100] The electrolytic stability of the composite diaphragm prepared in Example 1 and Comparative Example 2 was tested. Test conditions: nickel mesh as working electrode, 30wt% KOH aqueous solution as electrolyte solution, electrolyte temperature of 80°C, current density of 500mA / cm2, test is divided into 2 steps, 1) off-cell test: simulate the actual working conditions of the electrolytic cell, immerse the composite diaphragm prepared in Example 1 and Comparative Example 2 in 30wt% KOH aqueous solution, the solution temperature is 80°C, and immersion is more than 1500 hours. Test the electrolytic performance of the diaphragm before and after immersion and characterize the morphology of the diaphragm after immersion, the test results are shown in Figure 6 (a~c); 2). Test in the upper tank: The composite diaphragm prepared in Example 1 was installed in the electrolytic tank to electrolyze water, and a constant current of 500mA / cm2 was applied. The electrolysis lasted for more than 600 hours, and the voltage change of the electrolytic tank was monitored and recorded. The test results are shown in Figure 6 (d). It can be seen from the figure that after long-term hot alkali erosion, the composite membrane prepared by Example 1 has no obvious surface change (a), and the electrolytic performance is only slightly attenuated (c), while the composite membrane prepared by Comparative Example 2 has only a small amount of inorganic matter retained after long-term hot alkali erosion (b), and the electrolytic performance is greatly reduced (c). Further, the composite membrane prepared by Example 1 has no obvious surface change (a), and the electrolytic performance is only slightly attenuated (c), after long-term hot alkali erosion. 2 After working for 600 hours at the current density, the electrolytic performance did not decay (d), demonstrating excellent electrolytic stability.

[0101] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a high-performance alkaline water electrolysis composite diaphragm, characterized in that: The following steps are involved: S1, soaking the organic polymer matrix in a swelling solvent to obtain a swollen organic polymer matrix; S2, taking another swelling solvent and mixing it with the precursor aqueous solution to obtain a functional inorganic mother solution; S3, adding the organic polymer matrix swollen in step S1 to the functional inorganic mother solution in step S2 and letting it stand, in-situ growth reaction, washing and drying to obtain an organic-inorganic composite membrane, i.e., a high-performance alkaline water electrolysis composite membrane, and completing.

2. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 1, characterized in that: In step S1, the organic polymer matrix includes polyphenylene sulfide, polyethylene, polypropylene, polytetrafluoroethylene, polyetheretherketone, polyimide, and its existing form includes porous membrane, non-woven fabric, woven fabric, composite fabric; The swelling solvent includes N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and toluene; The volume ratio of the organic polymer matrix to the swelling solvent is 1:20-200.

3. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 1, characterized in that: In step S1, the organic polymer matrix is ​​heat treated at 25-100°C.

4. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 1, characterized in that: In step S2, the precursor aqueous solution is a mixed solution containing divalent metal cations, trivalent metal cations, and alkaline substances.

5. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 4, characterized in that: The divalent metal cations include Mg 2+ 、Zn 2+ 、Co 2+ 、Ni 2+ , Fe 2+ ; trivalent metal cations include Al 3+ , Fe 3+ ; Alkaline substances include sodium hydroxide, potassium hydroxide, urea, ammonia water, and hexamethylenetetramine; The concentration of the divalent metal cation is 0.02-1 mol / L, the concentration of the trivalent metal cation is 0.02-1 mol / L, and the concentration of the alkaline substance is 0.1-5 mol / L.

6. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 1, characterized in that: In step S2, the volume ratio of the swelling solvent to the precursor aqueous solution is 1:0.3-3; In step S3, the volume ratio of the swollen organic polymer matrix to the functional inorganic substance mother solution is 1:1 to 50; The in-situ growth reaction includes a co-precipitation method and a hot solvent method.

7. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 1, characterized in that: When the swelling solvent is immiscible with the precursor aqueous solution, the preparation method comprises the following steps: S1, soaking the organic polymer matrix in a swelling solvent to obtain a swollen organic polymer matrix, placing the organic polymer matrix in a medium solvent to replace the swelling solvent with the medium solvent, and obtaining a replaced organic polymer matrix; S2, taking another medium solvent and a precursor aqueous solution and mixing them to obtain a functional inorganic mother solution; S3, adding the organic polymer matrix replaced in step S1 to the functional inorganic mother solution in step S2 and letting it stand, in-situ growth reaction, washing and drying to obtain an organic-inorganic composite diaphragm, i.e., a high-performance alkaline water electrolysis composite diaphragm, and completing.

8. The method for preparing a high-performance alkaline water electrolysis composite diaphragm according to claim 7, characterized in that: The medium solvent is a solvent that is miscible with both the precursor aqueous solution and the swelling solvent, including ethanol, acetone, and tetrahydrofuran; In step S1, the volume ratio of the swollen organic polymer matrix to the medium solvent is 1:50-200; In step S2, the volume ratio of the precursor aqueous solution to the medium solvent is 1:0.3-3; In step S3, the volume ratio of the replaced organic polymer matrix to the functional inorganic substance mother liquid is 1:1-50.

9. A high-performance alkaline water electrolysis composite diaphragm, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the high-performance alkaline water electrolysis composite diaphragm as claimed in claim 9 in the field of alkaline water electrolysis hydrogen production.

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