High-toughness composite diaphragm for hydrogen production from alkaline electrolyzed water and preparation method of high-toughness composite diaphragm

Abstract

The invention relates to a high-toughness composite diaphragm for hydrogen production from alkaline electrolyzed water and a preparation method of the high-toughness composite diaphragm. The composite diaphragm is prepared from a main polymer, a toughening polymer, a pore forming agent, hydrophilic inorganic filler and a reinforcing framework. The composite diaphragm is long in service life and low in surface resistance in the high-temperature alkaline environment, the preparation process is simple, the cost is controllable, and the problem that a traditional composite diaphragm is prone to bending and cracking in the hydrogen production process is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and green hydrogen production technology, and specifically relates to a high-toughness alkaline water electrolysis hydrogen production composite membrane and its preparation method. Background Technology

[0002] Alkaline water electrolysis (ALK) has become the mainstream route for large-scale green hydrogen production due to its mature technology and low cost. Its core membrane needs to simultaneously achieve efficient OH⁻ conduction and strict H₂ / O₂ isolation. Currently, the mainstream industrial method uses a Zirfon-type membrane with a polysulfone (PSF)-ZrO₂ system reinforced with a PPS mesh. However, during long-term operation, the aromatic ether bonds in the polysulfone backbone are prone to hydrolysis, resulting in a mechanical strength decrease of >30% within 5000 hours; the high Tg (temperature resistance) leads to brittleness, causing assembly and thermal cycling cracking.

[0003] Chinese patent CN118390110B discloses a diaphragm for an alkaline hydrolysis cell and its preparation method. First, an inorganic framework is obtained by molding and sintering a mixture containing inorganic raw materials. Organic fillers are then infiltrated into the inorganic framework, followed by phase transformation to obtain the diaphragm for the alkaline hydrolysis cell. Chinese patent CN116377508A proposes a composite diaphragm for a water electrolysis cell. This involves mixing and granulating polyphenylene sulfide resin with zirconium oxide inorganic nanoparticles, drying the mixture, and then melt-spinning it to obtain zirconium oxide-modified PPS fibers. These fibers are then spun into yarn, woven into fabric, and subjected to hydroentangling to obtain a polyphenylene sulfide fabric-type alkaline water electrolysis diaphragm. These existing technologies focus on improving the chemical stability, gas permeability, high-temperature resistance, ion conductivity, and service life of the diaphragm, but they do not solve the problem of traditional composite membranes being prone to bending and cracking during hydrogen production. Summary of the Invention

[0004] The purpose of this invention is to provide a high-toughness composite membrane for hydrogen production via alkaline water electrolysis and its preparation method, in order to solve the technical problems of existing alkaline water electrolysis membranes, such as insufficient toughness, short lifespan, complex processes, or cracking when bent under strong alkaline and high-temperature conditions.

[0005] This invention provides a high-toughness composite membrane for hydrogen production via alkaline water electrolysis. The composite membrane is composed of a main polymer, a toughening polymer, a pore-forming agent, a hydrophilic inorganic filler, and a reinforcing skeleton. The main polymer and the toughening polymer form an interpenetrating network structure through inter-chain hydrogen bonds and microphase separation, thereby improving the elongation at break.

[0006] Preferably, the host polymer includes, but is not limited to, at least one of polysulfone (PSU), polyphenylene sulfide (PPS), or polyether ether ketone (PEEK).

[0007] Preferably, the toughening polymer includes, but is not limited to, at least one of polyphenylene sulfone (PES-C), polyether sulfone (PES-K), polyamide (PA), sulfonated polysulfone (SPSU), sulfonated polyether sulfone (SPES), or sulfonated polyphenylene sulfone (SPPSU); the degree of sulfonation of the sulfonated polysulfone, sulfonated polyether sulfone, or sulfonated polyphenylene sulfone is 20%-60%, and the polar groups introduced therein generate strong interfacial interactions with the host polymer, promoting compatibility and inhibiting large-scale phase separation.

[0008] Preferably, the pore-forming agent includes, but is not limited to, at least one of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), lithium chloride (LiCl), or sodium chloride (NaCl).

[0009] Preferably, the hydrophilic inorganic filler includes, but is not limited to, at least one of titanium dioxide (TiO2), zirconium oxide (ZrO2), or boehmite (AlOOH).

[0010] Preferably, the reinforcing skeleton is a three-dimensional mesh support structure woven from alkali-resistant high-strength polymer monofilaments; the alkali-resistant high-strength polymer includes at least one of polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), or polyethersulfone (PES).

[0011] This invention also provides a method for preparing the above-mentioned high-toughness alkaline water electrolysis hydrogen production composite membrane, comprising the following steps: (1) The main polymer, toughening polymer and pore-forming agent are co-dissolved in an organic solvent to form a homogeneous casting solution; then hydrophilic inorganic filler is added to the homogeneous casting solution, and the coating slurry is obtained by stirring and degassing. (2) Pour the coating slurry obtained in step (1) into the material tank and perform slit coating on the reinforcing skeleton to obtain the initial wet film; (3) Perform steam bath pre-evaporation treatment on the nascent wet film from step (2); (4) The nascent wet membrane after step (3) is sequentially immersed in the first coagulation bath and the second coagulation bath for phase separation to form a nascent composite membrane. Then it is washed with deionized water to obtain a composite membrane.

[0012] Preferably, in step (1), the mass ratio of the main polymer: toughening polymer: pore-forming agent: hydrophilic inorganic filler is 4: (1-3): (3-4): (27-34).

[0013] Preferably, in step (2), the slit width is 0.3-0.6 mm and the coating speed is 0.5-2 m / min.

[0014] Preferably, in step (3), the nascent wet film is placed in an environment with a relative humidity of 40%-80% and a temperature of 25-60°C for 10-300 seconds for pre-evaporation in a steam bath.

[0015] Preferably, in step (4), the first coagulation bath is an N-methylpyrrolidone / water mixture or an ethanol / water mixture, wherein the mass fraction of N-methylpyrrolidone or ethanol is 20%-60%; the second coagulation bath is deionized water; the residence time of the nascent wet film in the first coagulation bath is 1-5 minutes, and the residence time in the second coagulation bath is 5-30 minutes.

[0016] Beneficial effects

[0017] The interpenetrating network structure formed by the toughening polymer and the host polymer in this invention endows the composite diaphragm with excellent toughness. Even in high-temperature alkaline environments, the composite diaphragm maintains excellent transverse tear strength and extremely high toughness retention, showing no cracks after repeated bending. This high toughness enables the composite diaphragm to withstand complex mechanical stresses in practical applications, maintaining structural integrity and performance stability, thereby significantly improving the reliability and service life of the overall system. Attached Figure Description

[0018] Figure 1 This is an image of the composite diaphragm prepared in Example 1 of the present invention.

[0019] Figure 2 This is a diagram showing the state of the composite diaphragm prepared in Example 1 of the present invention after bending.

[0020] Figure 3 This is a diagram showing the state of the composite diaphragm prepared in Comparative Example 1 of the present invention after bending. Detailed Implementation

[0021] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0022] The test methods and standards for various performance aspects of the composite membranes in the examples and comparative examples are as follows: (1) Composite diaphragm swelling rate test: The swelling rate of the composite diaphragm is determined by the alkaline immersion absorption test method according to ISO 138 standard. The diaphragm is cut into square samples with sides of 2 cm, and its dry mass m3 is weighed. The samples are then immersed in a suitable solvent for 24 hours. After immersion, the samples are removed, excess solvent is absorbed with filter paper, and their mass m4 is quickly weighed. The swelling rate is calculated using the formula: , Where m3 is the initial mass (g) of the composite membrane. m4 is the mass (g) of the composite membrane after solvent absorption.

[0023] (2) Composite diaphragm bending test: The composite diaphragm sample is fixed on a dedicated bending test device, and the sample is repeatedly bent at a certain radius of curvature until cracks, fractures or other failures occur. The number of bends is recorded to evaluate the bending fatigue resistance of the composite diaphragm.

[0024] Example 1

[0025] This embodiment provides a high-toughness composite membrane for alkaline water electrolysis to produce hydrogen, the preparation method of which includes the following steps: (1) Polysulfone (PSU), polyphenylsulfone (PPSU) and polyvinylpyrrolidone (PVP) are co-dissolved in N-methylpyrrolidone (NMP) to form a homogeneous casting solution; then zirconium oxide is added to the homogeneous casting solution in proportion and stirred to disperse it evenly to obtain a coating slurry; wherein, the mass ratio of polysulfone (PSU): polyphenylsulfone (PPSU): polyvinylpyrrolidone (PVP): zirconium oxide is 4:2.6:4:34; (2) The coating slurry was coated onto a 60-mesh, 0.25 mm thick PPS screen using a slot coating method. The slot width was 0.6 mm and the coating speed was 1.5 m / min. (3) The nascent wet film from step (2) was placed in an environment with a relative humidity of 50% and a temperature of 50°C for 60 seconds for pre-evaporation in a steam bath; (4) The nascent wet membrane treated in step (3) is sequentially immersed in a 20% ethanol / water mixture (5 minutes) and deionized water (10 minutes) for phase separation to form a nascent composite membrane. It is then washed with deionized water to obtain composite membrane M1, as shown below. Figure 1 As shown.

[0026] Example 2

[0027] This embodiment provides a high-toughness composite membrane for alkaline water electrolysis to produce hydrogen. Its preparation method is the same as in Example 1, except that in step (1), the mass ratio of polysulfone (PSU) to polyphenylene sulfone (PPSU) is 4:2.5. The composite membrane M2 is thus obtained.

[0028] Example 3

[0029] This embodiment provides a high-toughness alkaline water electrolysis hydrogen production composite membrane, which is prepared in the same way as in Example 2, except that in step (1), polyphenylene sulfone (PPSU) is replaced with sulfonated polysulfone (SPSF) (sulfonation degree 20%). Composite membrane M3 is obtained.

[0030] Comparative Example 1

[0031] This comparative example provides a composite membrane, which is prepared in the same way as in Example 1, except that the toughening polymer polyphenylsulfone (PPSU) is not added in step (1). The composite membrane M4 is obtained.

[0032] The composite membranes prepared in Examples 1-3 and Comparative Example 1 were subjected to swelling rate and bending tests, and the experimental results are shown in Table 1. With the addition of the toughening polymer PPSU, the swelling rate of the composite membrane decreased, further improving the mechanical integrity of the membrane. The polar groups introduced by sulfonated polysulfone generate strong interfacial interactions with polysulfone, promoting compatibility and inhibiting large-scale phase separation. By controlling the proportion of the toughening polymer, a high-toughness alkaline water electrolysis hydrogen production composite membrane with no cracks after 1000 bends can be obtained. Composite membrane M1 maintained its intact and smooth shape after the bending test, without any cracks. Figure 2 As shown; in Comparative Example 1, the composite diaphragm without the addition of toughening polymer PPSU showed obvious cracking after bending, as... Figure 3 As shown.

[0033] Table 1. Results of swelling rate and bending test of the composite membranes prepared in Examples 1-3 and Comparative Example 1.

[0034] In summary, this invention uses a high-temperature and strong-alkali resistant main polymer and introduces a toughening phase to achieve a one-step film formation technology using non-solvent-induced phase separation. This enables the composite membrane to have a long service life and low sheet resistance in high-temperature and alkaline environments. Furthermore, the preparation process is simple and cost-controllable, effectively solving the problem of traditional composite membranes being prone to bending and cracking during hydrogen production.

Claims

1. A composite separator for hydrogen production by high-tenacity alkaline electrolysis of water, characterized by comprising a porous polymer layer and a porous inorganic layer. The composite diaphragm is composed of a main polymer, a toughening polymer, a pore-forming agent, a hydrophilic inorganic filler and a reinforcing framework.

2. The composite separator for hydrogen production by alkaline water electrolysis with high toughness according to claim 1, characterized by, The main polymer comprises at least one of polysulfone, polyphenylene sulfide or polyether ether ketone.

3. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The toughening polymer comprises at least one of polyphenyl sulfone, polyether sulfone, polyamide, sulfonated polysulfone, sulfonated polyether sulfone or sulfonated polyphenyl sulfone; wherein the sulfonation degree of the sulfonated polysulfone, sulfonated polyether sulfone or sulfonated polyphenyl sulfone is 20%-60%.

4. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The pore-forming agent comprises at least one of polyvinylpyrrolidone, polyethylene glycol, lithium chloride or sodium chloride; and the hydrophilic inorganic filler comprises at least one of titanium dioxide, zirconium oxide or boehmite.

5. The composite separator for hydrogen production by alkaline water electrolysis according to claim 1, characterized by, The reinforcing framework is a three-dimensional net-like support structure woven by alkali-resistant high-strength polymer monofilaments; and the alkali-resistant high-strength polymer comprises at least one of polyphenylene sulfide fiber, polytetrafluoroethylene fiber or polyether sulfone fiber.

6. A preparation method of a high-toughness composite diaphragm for hydrogen production by alkaline electrolysis of water, comprising the following steps: (1) dissolving a main polymer, a toughening polymer and a pore-forming agent in an organic solvent to form a homogeneous casting solution; then adding a hydrophilic inorganic filler to the homogeneous casting solution, and stirring and defoaming to obtain a coating slurry; (2) pouring the coating slurry obtained in step (1) into a trough to perform slot coating on a reinforcing framework, and obtaining a nascent wet film; (3) performing steam bath pre-evaporation treatment on the nascent wet film obtained in step (2); (4) immersing the nascent wet film treated in step (3) in a first coagulation bath and a second coagulation bath in sequence for phase separation, forming a nascent composite diaphragm, and then washing with deionized water to obtain the composite diaphragm.

7. The production method according to claim 6, wherein In step (1), the mass ratio of the main polymer, the toughening polymer, the pore-forming agent and the hydrophilic inorganic filler is 4: (1-3): (3-4): (27-34).

8. The production method according to claim 6, characterized by, In step (2), the slot width is 0.3-0.6 mm, and the coating speed is 0.5-2 m / min.

9. The preparation method according to claim 6, characterized in that, In step (3), the nascent wet film is placed in an environment with a relative humidity of 40%-80% and a temperature of 25-60°C for 10-300 seconds for steam bath pre-evaporation.

10. The method of claim 6, wherein, In step (4), the first coagulation bath is an N-methylpyrrolidone / water mixture or an ethanol / water mixture, wherein the mass fraction of N-methylpyrrolidone or ethanol is 20%-60%; the second coagulation bath is deionized water; and the nascent wet film stays in the first coagulation bath for 1-5 minutes and stays in the second coagulation bath for 5-30 minutes.

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