Composite diaphragm for hydrogen production from alkaline electrolyzed water, and preparation method and application thereof

Abstract

The invention belongs to the technical field of diaphragms for hydrogen production, and particularly relates to a composite diaphragm for hydrogen production by alkaline electrolyzed water as well as a preparation method and application. An organic-inorganic composite coating covers a supporting net of the composite diaphragm, and the composite diaphragm is characterized in that the organic-inorganic composite coating at least contains an organic polymer binder, inorganic hydrophilic particles and a hydrogen bond organic framework material. According to the composite diaphragm, the aperture of the diaphragm can be remarkably reduced by using the hydrogen bond organic framework material, the surface resistance and alkali loss rate are reduced, and the air tightness is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen production diaphragm, and particularly relates to a composite diaphragm for hydrogen production by alkaline electrolysis of water and a preparation method and application thereof. BACKGROUND

[0002] The hydrogen production by alkaline electrolysis of water is the most suitable large-scale application technology among various hydrogen production technologies, and has the advantages of simple tank structure, safety and reliability, and low price. The diaphragm plays a role in avoiding mixing of gases from two poles and ensuring ion conduction path in the hydrogen production equipment. The environment and function of the electrolysis reaction require the diaphragm to have good support, corrosion resistance, air tightness, hydrophilicity and ion conductivity.

[0003] The commercial hydrogen production diaphragm by alkaline electrolysis of water has undergone three generations of development. The first generation is asbestos diaphragm, which has been eliminated due to its high swelling and other defects. The second generation is polyphenylene sulfide (PPS) diaphragm, which has good mechanical properties and corrosion resistance and is the current mainstream technology, but has high surface resistance and insufficient gas barrier performance, resulting in low electrolysis tank efficiency and insufficient safety. The third generation is a composite diaphragm, which usually coats a hydrophilic layer (including a chemically inert polymer base and a hydrophilic inorganic filler) on a porous support layer (PPS mesh) to form a porous composite diaphragm. For example, the composite diaphragm with organic-inorganic coating provided in CN115928145A and CN120384308A.

[0004] However, most of the current composite diaphragms still have the following problems: (1) the hydrophobicity of the polyphenylene sulfide (PPS) mesh is strong, and the ion conduction of the composite diaphragm mainly depends on the porous structure in the hydrophilic layer, but the chemically inert polymer base still causes the diaphragm to have low hydrophilicity, high resistance and high hydrogen production energy consumption; (2) the membrane pores cause the bubble point pressure of the membrane to decrease, and the hydrogen and oxygen generated by electrolysis are prone to permeate and mix, resulting in an increase in electrolysis voltage and a decrease in the purity of the collected gas; (3) the physical force between the inorganic filler in the hydrophilic layer and the polymer base is weak, which causes the inorganic filler to easily fall off during use, endangering the long-term stable operation of the electrolysis tank equipment.

[0005] Therefore, it is urgent to provide a new type of composite diaphragm that has high gas barrier performance and long-term stability while ensuring excellent ion conduction capability. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a composite diaphragm for hydrogen production by alkaline electrolysis of water and a preparation method and application thereof. The technical solution of the present application is as follows: A composite diaphragm for hydrogen production by alkaline electrolysis of water is composed of a support mesh and organic-inorganic composite coatings coated on both sides of the support mesh, and the organic-inorganic composite coatings contain a polymer binder, hydrophilic inorganic nanoparticles and hydrogen-bonded organic framework materials.

[0007] Preferably, the organic structural units of the hydrogen-bonded organic framework material are selected from one or more of aromatic groups, porphyrin groups, and metal complexes; the hydrophilic groups of the hydrogen-bonded organic framework material are selected from one or more of phosphate groups, carboxyl groups, sulfonic acid groups, amine groups, imidazole groups, and guanidine groups.

[0008] The hydrogen bond donor and acceptor molecules of the hydrogen-bonded organic framework material may be the same molecule or different molecules. Preferably, the hydrogen bond donor of the hydrogen-bonded organic framework material is selected from one or more of guanidinium ions, trans-1,4-cyclohexanediamine, p-phenylenediamine, 1,3,5-tris(4-carboxyphenyl)benzene, diaminotriazine, and [9,9'-bicarbazole]-3,3',6,6'-tetracarboxynitrile; the hydrogen bond acceptor of the hydrogen-bonded organic framework material is selected from one or more of 4,4'-biphenyl disulfonic acid, 1,5-naphthalene disulfonic acid, tetra(4-sulfophenyl)methane, 1,3,5-tris(4-carboxyphenyl)benzene, diaminotriazine, and [9,9'-bicarbazole]-3,3',6,6'-tetracarboxynitrile.

[0009] Preferably, the thickness of the support mesh is 50 μm to 300 μm; the thickness of one side of the organic-inorganic composite coating is 100 to 500 µm; and the particle size of the hydrophilic inorganic nanoparticles is 20 nm to 200 nm.

[0010] Preferably, the mass ratio of the polymer binder to the hydrophilic inorganic nanoparticles is 1:(1~6); the mass ratio of the hydrogen-bonded organic framework material to the polymer binder is 1:(1.5~11).

[0011] The aforementioned method for preparing the composite membrane includes the following steps: S1 dissolves the polymer binder to form a polymer binder solution; S2 disperses hydrophilic inorganic nanoparticles and hydrogen-bonded organic framework materials in the above polymer binder solution, and adds a pore-forming agent to form a film-forming slurry.

[0012] S3 applies the membrane-forming slurry to the support mesh to prepare a composite membrane coated with an organic-inorganic composite coating.

[0013] The aforementioned composite membrane is used as a hydrogen production membrane in an alkaline water electrolysis hydrogen production device.

[0014] Beneficial effects

[0015] Compared to existing technologies, the composite diaphragm of this invention allows the electrolyte to fill the micropores of the organic-inorganic composite coating containing a hydrogen-bonded organic framework material, promoting hydroxide ion conduction and reducing the sheet resistance of the composite diaphragm. The hydrogen-bonded organic framework material also significantly reduces the size of the organic-inorganic composite coating, greatly improving the bubble point pressure and gas barrier properties of the composite diaphragm, thereby enhancing the gas purity and operational reliability of the electrolyzer. Furthermore, the hydrophilic groups in the hydrogen-bonded organic framework material form hydrogen bonds with the hydrophilic inorganic nanoparticles, while the reduced pore size confines the hydrophilic inorganic nanoparticles, preventing their shedding during long-term use and improving the long-term operational stability of the electrolyzer. Attached Figure Description

[0016] Figure 1 Typical XRD patterns of the diaphragm samples from Experimental Example 6 and Comparative Example 1. Detailed Implementation

[0017] This invention provides a composite membrane for hydrogen production via water electrolysis, applicable to an alkaline water electrolysis hydrogen production device. The composite membrane includes a support mesh and an organic-inorganic composite coating. The organic-inorganic composite coating includes three components: a polymer binder, hydrophilic inorganic nanoparticles, and a hydrogen-bonded organic framework (HOF) material.

[0018] The present invention does not specifically limit the material of the support mesh used for the diaphragm. For example, the support mesh can be any one of polyphenylene sulfide (PPS) fabric, polyether ether ketone (PEEK) fabric, liquid crystal polymer (LCP) fabric, polyethylene (PE) fabric, polypropylene (PP) fabric, etc.

[0019] This invention does not specifically limit the polymer binder used in the organic-inorganic composite coating of the diaphragm. For example, the polymer binder may include any one or a combination of polysulfone (PSU), polyethersulfone (PES), polyphenylene ethersulfone (PPSU), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), and polyether ether ketone (PEEK).

[0020] This invention does not specifically limit the hydrophilic inorganic nanoparticles used in the organic-inorganic composite coating of the diaphragm. For example, the aforementioned hydrophilic inorganic nanoparticles can be any one or a combination of zirconium oxide, titanium oxide, cerium oxide, zinc oxide, and aluminum oxide. The preferred particle size of the hydrophilic inorganic nanoparticles is 20-200 nm.

[0021] HOF materials are organic molecular units in which hydrogen bond donors and acceptors are linked by hydrogen bond interactions. This invention does not specifically limit the hydrogen bond donor and acceptor materials used in the HOF within the aforementioned organic-inorganic composite coating. For example, the organic structural units in the molecules of the aforementioned hydrogen-bonded organic framework materials include, but are not limited to, aromatic groups, porphyrin groups, and metal complexes; the hydrophilic groups include, but are not limited to, phosphate groups, carboxyl groups, sulfonic acid groups, amine groups, imidazole groups, and guanidine groups. This invention does not limit the molar ratio of hydrogen bond donors and acceptors used in the HOF; for example, the molar ratio of hydrogen bond donors and acceptors is 1:(1~4).

[0022] This invention provides a method for preparing the above-mentioned composite separator. The preparation method includes: S1 dissolves the polymer binder to form a polymer binder solution; S2 contains a pore-forming agent, hydrophilic inorganic nanoparticles, and hydrogen-bonded organic framework materials dispersed in the above polymer binder solution to form a film-forming slurry.

[0023] S3 applies the membrane-forming slurry to the support mesh to prepare a composite membrane with an organic-inorganic composite coating.

[0024] This invention does not specifically limit the solvent used to prepare the polymer binder solution. Exemplary examples include, but are not limited to, any one or a combination of N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), N-butylpyrrolidone (NBP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO); or the above solvents may include non-solvent components, such as N-methylpyrrolidone and water, ethanol, isopropanol, diethyl ether, etc.

[0025] The present invention does not specifically limit the concentration of the above-mentioned polymer binder solution. For example, the mass fraction of the polymer binder in the solution can be 10% to 25%, specifically 10%, 15%, 17%, 20%, 24%, etc.

[0026] This invention does not specifically limit the method for applying the film-forming slurry to the support mesh for composite coating. For example, the film-forming slurry can be coated onto the support mesh and then cured through phase inversion or other methods to form an organic-inorganic composite coating. Alternatively, the support mesh can be immersed in the film-forming slurry and then cured through phase inversion or other methods to form an organic-inorganic composite coating.

[0027] This invention does not specifically limit the above-described phase transformation steps. For example, the above-described phase transformation steps can be: After the support mesh coated with the film-forming slurry is exposed to air for a certain period of time, it is immersed in a coagulation bath for non-solvent-induced phase separation (NIPS), which allows the film-forming slurry to solidify and form an organic-inorganic composite coating. Alternatively, the support mesh coated with the film-forming slurry is subjected to vapor-induced phase separation (VIPS) treatment in a vertical direction.

[0028] This invention does not specifically limit the exposure time of the support mesh coated with film-forming slurry before the above-mentioned NIPS process in the air. For example, the exposure time of the support mesh coated with film-forming slurry in the air may include 0-12h. More specifically, the exposure time of the support mesh coated with film-forming slurry in the air may include 0-1h. In other words, the exposure time of the support mesh coated with film-forming slurry in the air may be 0h, 0.2h, 0.5h, or 1h, etc.

[0029] The present invention does not specifically limit the composition of the coagulation bath in the above-mentioned NIPS process. For example, the coagulation bath can be a non-solvent, such as any one or a combination of water, ethanol, propanol, dichloromethane, etc.; or the coagulation bath can be a mixture of non-solvent and solvent, such as a coagulation bath composed of water and N,N-dimethylacetamide, N,N-dimethylformamide, etc.

[0030] This invention does not specifically limit the temperature of the coagulation bath in the above-described NIPS process. For example, the temperature range of the coagulation bath may include -5℃ to 50℃. Furthermore, the temperature range of the coagulation bath may include 5℃ to 25℃, specifically, the temperature of the coagulation bath may be 5℃, 8℃, 10℃, 15℃, 20℃, or 25℃, etc.

[0031] This invention does not specifically limit the non-solvent vapor in the aforementioned VIPS process. For example, the non-solvent vapor may include water vapor, ethanol vapor, propanol vapor, etc. Furthermore, water vapor can be used, which is low-cost and environmentally friendly. The flow rate of the water vapor can be controlled by a water vapor generator, and the microporous structure of the organic-inorganic composite coating can be adjusted by changing the flow rate and temperature of the water vapor.

[0032] This invention does not specifically limit the temperature of the water vapor in the aforementioned VIPS process. For example, the temperature range of the water vapor can include 30℃ to 90℃, specifically, the temperature can be 30℃, 40℃, 60℃, 70℃, or 90℃, etc. Further, the temperature range of the water vapor can include 50℃ to 60℃, specifically, the temperature can be 50℃, 54℃, 46℃, or 60℃, etc.

[0033] This invention does not specifically limit the time of the aforementioned VIPS process. For example, the VIPS process time can range from 0.01 h to 1 h, specifically, the VIPS process time can be 15 s, 1 min, 10 min, 30 min, or 60 min, etc. Further, the VIPS process time range can range from 0.05 h to 10 min, specifically, the VIPS process time can be 15 s, 1 min, 5 min, or 10 min, etc.

[0034] The technical concept, solution, and effects of the present invention will be described in detail below through specific embodiments. These embodiments are merely illustrative examples and should not be considered as limiting the scope of protection of the present invention. In the following embodiments and comparative examples, the zirconium oxide used in the composite membranes is uniformly selected with a particle size of 70±20 nm.

[0035] Example 1: Experimental Composite Separator and its Preparation This embodiment provides 8 different experimental composite membranes. The support mesh is selected as polyphenylene sulfide fabric (NBCMeshtec inc. PPS177 / 70, pore size 177µm, open porosity 70%, mesh size 120). The material composition of the organic-inorganic composite coating is shown in Table 1 (where the molar ratio of hydrogen bond donor to acceptor is 1:1).

[0036] Table 1. Material composition of the organic-inorganic composite coating in the composite membrane of the experimental example.

[0037] In Table 1: % represents the mass fraction.

[0038] The preparation methods of the composite membranes in the eight experimental examples are as follows: 1) At 40°C, polysulfone was dissolved in N,N-dimethylacetamide to prepare a polysulfone solution with a mass concentration of 20%. 2) At room temperature, zirconium oxide and hydrogen-bonded organic framework material are dispersed in the above solution, and a pore-forming agent (glycerol, amount of 0.5% of polysulfone mass) is added and stirred for 0.5 h to obtain a film-forming slurry.

[0039] 3) Apply the film-forming slurry to the upper and lower surfaces of the polyphenylene sulfide support mesh by scraping, with a coating amount of 110 mg / cm². 2 (At this point, the film-forming slurry covers the upper and lower surfaces of the support mesh and fills some or all of the through-holes in the support mesh). Pre-evaporate at 40°C for 15 min, then perform steam-induced phase separation treatment on the support mesh coated with the film-forming slurry in the vertical direction. The steam temperature used is 50°C, and the treatment time is 1 min. After that, immerse it in deionized water at 15°C for 15 min to carry out phase inversion.

[0040] 4) Soak the membrane obtained in step 3) in deionized water at 50°C for 5 hours to remove the residual solvent in the membrane and obtain a composite membrane.

[0041] The thickness of the organic-inorganic composite coating of the composite membrane in the 8 experimental examples was about 300µm (the coating thickness on one side of the support mesh, the thickness on both sides was the same, that is, the coating thickness on both sides was about 600µm).

[0042] Example 2: Comparative Composite Separator and its Preparation The only difference between the comparative composite membrane and the experimental composite membrane is that no hydrogen-bonded organic framework material is added during the preparation (the material composition of the organic-inorganic composite coating is shown in Table 2). Table 2. Composition of organic-inorganic composite coatings in comparative composite membranes

[0043] In Table 2: % represents the mass fraction.

[0044] Example 3: Comparative Tests of Composite Separators in Experimental and Comparative Examples 1. Pore size distribution of composite membranes According to GB / T 32361-2015 ("Separation Membrane Pore Size Test Method: Bubble Point and Average Flow Rate Method"), the pore size distribution of the above experimental example and comparative example composite membranes was tested, and the results are shown in Table 3 below.

[0045] Table 3. Pore size distribution of different composite membranes (unit: nm)

[0046] As shown in Table 3, the addition of hydrogen-bonded organic framework materials significantly reduces the pore size of the composite membrane.

[0047] 2. Performance and stability parameters of composite diaphragms According to SJ / T 10171-2016 (General Test Method for Basic Performance of Alkaline Battery Separator) and GB T 32361-2015 (Test Method for Separator Pore Size, Bubble Point and Average Flow Rate Method), the surface resistivity, bubble point pressure and alkali loss of the above experimental example and comparative example composite separators were tested, and the results are shown in Table 4 below.

[0048] Table 4 Performance and stability parameters of different composite membranes

[0049] Table 4 shows that the addition of hydrogen-bonded organic framework materials significantly reduces the sheet resistivity of the composite membrane, significantly increases the bubble point pressure, significantly decreases the alkali loss, and significantly reduces the amount of zirconium oxide detachment. These changes become more pronounced when the amount of hydrogen-bonded organic framework material added increases.

[0050] In addition, X-ray diffraction (XRD) analysis was performed on the aforementioned diaphragm. Figure 1 The images show typical XRD patterns of the membrane samples from Experimental Example 6 and Comparative Example 1. As can be seen from the spectra, when the ratio of polymer binder to hydrophilic inorganic nanoparticles is close, the membrane of Experimental Example 6 shows a new peak at 2-Theta≈5.2°, indicating that a hydrogen-bonded organic framework has been formed in the membrane.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A composite separator for hydrogen production by alkaline electrolysis of water, composed of a support mesh and an organic-inorganic composite coating layer applied to both sides of the support mesh, characterized in that, The organic-inorganic composite coating contains a polymer binder, hydrophilic inorganic nanoparticles, and a hydrogen-bonding organic framework material.

2. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by The organic structural units of the hydrogen-bonding organic framework material are selected from one or more of an aromatic group, a porphyrin group, and a metal complex.

3. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The hydrophilic groups of the hydrogen-bonding organic framework material are selected from one or more of a phosphoric acid group, a carboxyl group, a sulfonic acid group, an amine group, an imidazole group, and a guanidine group.

4. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The hydrogen-bonding donors of the hydrogen-bonding organic framework material are selected from one or more of a guanidinium ion, trans-1,4-cyclohexanediamine, p-phenylenediamine, 1,3,5-tris(4-carboxyphenyl)benzene, diaminotriazine, and [9,9'-biscarbazole]-3,3',6,6'-tetracyanide.

5. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The hydrogen-bonding acceptors of the hydrogen-bonding organic framework material are selected from one or more of 4,4'-diphenyldisulfonic acid, 1,5-naphthalenedisulfonic acid, tetra(4-sulfophenyl)methane, 1,3,5-tris(4-carboxyphenyl)benzene, diaminotriazine, and [9,9'-biscarbazole]-3,3',6,6'-tetracyanide.

6. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by The thickness of the support net is 50 µm to 300 µm.

7. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The single-sided thickness of the organic-inorganic composite coating is 100 µm to 500 µm.

8. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The mass ratio of the polymer binder to the hydrophilic inorganic nanoparticles is 1:(1 to 6), and the mass ratio of the hydrogen-bonding organic framework material to the polymer binder is 1:(1.5 to 11).

9. The method of claim 1 to 8, wherein the method is characterized by, The method comprises the following steps: S1 dissolving a polymer binder to form a polymer binder solution; S2 dispersing hydrophilic inorganic nanoparticles and a hydrogen-bonding organic framework material in the polymer binder solution, and adding a pore-forming agent for pore formation to form a film-forming slurry; S3 applying the film-forming slurry to a support net to prepare a composite separator coated with an organic-inorganic composite coating.

10. Use of the composite separator for hydrogen production by alkaline electrolysis of water according to any one of claims 1 to 8 or prepared by the preparation method of claim 9 as a hydrogen production separator for an alkaline electrolysis of water hydrogen production device.

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