A method for preparing a polyphenylene sulfide alkaline water electrolysis membrane

Abstract

This invention relates to a method for preparing a polyphenylene sulfide (PPS) alkaline water electrolysis membrane, comprising the following steps: (1) washing and drying the PPS woven membrane fabric in deionized water and ethanol successively; (2) immersing the PPS woven membrane fabric obtained in step (1) in a haloalkane solvent, removing and drying for later use; (3) immersing the PPS woven membrane fabric obtained in step (2) in a good organic solvent of PPS under ultrasonic conditions; (4) subjecting the impregnated PPS woven membrane fabric obtained in step (3) to a sulfonation reaction, washing, and drying to obtain a hydrophilic modified PPS alkaline water electrolysis membrane. This invention improves the hydrophilicity of the PPS membrane and reduces its sheet resistance by performing a two-step impregnation treatment on the PPS woven membrane fabric followed by a sulfonation reaction; moreover, the sheet resistance remains stable even after prolonged immersion in a high-temperature alkaline electrolyte environment.

Description

Technical Field

[0001] This invention belongs to the field of polyphenylene sulfide polymers, and specifically relates to a method for preparing a polyphenylene sulfide alkaline water electrolysis membrane. Background Technology

[0002] Currently, existing water electrolysis technologies for hydrogen production mainly include four types: alkaline aqueous solution electrolysis (ALK), proton exchange membrane electrolysis (PEM), high-temperature solid oxide electrolysis (SOEC), and solid polymer anion exchange membrane electrolysis (AEM). Proton exchange membrane electrolysis has advantages such as high electrolysis current density, high efficiency, and fast response speed. However, in acidic media, it cannot avoid the use of expensive precious metal catalysts (such as Pt and IrO2) and titanium-based bipolar plates, and the high cost limits the large-scale application of proton exchange membrane water electrolysis. In contrast, in alkaline media, it can utilize inexpensive non-precious metals (such as Fe, Co, and Ni) as catalysts and avoid the use of expensive titanium-based components. High-temperature solid oxide electrolysis and solid polymer anion exchange membrane electrolysis technologies are still immature, and their production scale needs to be improved. Therefore, developing alkaline water electrolysis technology for hydrogen production is beneficial to significantly reduce the cost of large-scale hydrogen production.

[0003] Alkaline water electrolysis for hydrogen production refers to the process of producing hydrogen by electrolyzing water in an alkaline electrolyte environment, typically a 30% KOH solution. In alkaline water electrolysis for hydrogen production, the diaphragm is a crucial component of the alkaline electrolyzer, serving three main functions: ① separating the cathode and anode to form cathode and anode chambers, preventing short circuits; ② preventing the mixing of hydrogen and oxygen generated at the electrodes, thus avoiding potential hazards; ③ possessing high porosity to facilitate the transfer of hydroxide ions from the cathode to the anode. Therefore, an ideal diaphragm material should possess the following characteristics: 1. High porosity, facilitating hydroxide ion transfer; 2. High gas barrier properties, preventing the mixing of hydrogen and oxygen generated during electrolysis; 3. High hydrophilicity and low resistivity; 4. High corrosion resistance, remaining stable in a 30% KOH solution electrolyte; 5. Thin thickness, small pore size, high mechanical strength, and good dimensional stability; 6. Low cost and long service life.

[0004] Commercially available membrane materials for alkaline electrolyzers are primarily porous membranes. These porous membranes themselves are not conductive; ion conduction relies mainly on the electrolyte filling the pores within the material. Asbestos membranes were the earliest commercially available alkaline membrane material, but due to their carcinogenicity, they have been gradually phased out. Currently, polyphenylene sulfide (PPS) is mostly used to replace asbestos as the membrane material for alkaline electrolyzers. PPS is a non-crystalline thermoplastic resin produced through a condensation reaction of p-dichlorobenzene and sodium sulfide, possessing high temperature resistance, good mechanical strength and thermal stability, and excellent physicochemical properties. However, PPS fabric has very low hydrophilicity; using only PPS fabric as the membrane for alkaline water electrolysis will result in excessive internal resistance within the electrolyzer. Therefore, it is necessary to improve the hydrophilicity of PPS fabric. Currently, there are two main methods for modifying PPS fabric: one is to coat the surface of the PPS fabric with a functional coating to improve its hydrophilicity, forming a composite membrane with a sandwich-like structure. However, under long-term operation, the inorganic deposit layer of the composite membrane will peel off, leading to a decline in performance. Another approach is to chemically treat PPS to insert hydrophilic functional groups (-SO3H, -C=O, etc.) onto the polyphenylene sulfide molecular chain.

[0005] CN115084611A discloses a sulfonated polyphenylene sulfide proton exchange membrane and its preparation method. The method involves reacting polyphenylene sulfide and a proton exchange resin in a polar solvent, removing excess solvent and impurities, and then adding a sulfide to continue the reaction, forming the sulfonated polyphenylene sulfide proton exchange resin. However, the synthesized sulfonated polyphenylene sulfide proton exchange resin requires quality evaluation, which is a rather cumbersome process.

[0006] CN113862821A discloses a polyphenylene sulfide (PPS) fiber fabric type alkaline water electrolysis membrane. This involves spinning and weaving zirconium oxide-modified PPS fibers, resulting in good hydrophilicity. However, this patent uses a blend of PPS resin and zirconium oxide inorganic nanoparticles, granulated, and then spun to weave the PPS membrane. This physical blending easily leads to phase separation and poor fusion, resulting in uneven hydrophilicity on the PPS membrane surface after spinning and weaving. Chemical grafting can avoid this phenomenon.

[0007] CN11133130A discloses a method for hydrophilicating polyphenylene sulfide resin, which involves electrolyzing sulfuric acid to produce persulfate, and using the strong oxidizing effect of persulfate to treat the surface of PPS resin. The hydrophilicity of the PPS resin surface is adjusted by adjusting the sulfuric acid concentration.

[0008] The aforementioned patents modify the surface of polyphenylene sulfide through grafting, sulfonation, and other treatments to be hydrophilic, but the interior remains hydrophobic. It is unstable under high-temperature alkaline water electrolysis conditions and cannot withstand the high-temperature alkaline electrolysis environment for a long time. During use, the membrane performance gradually declines and the lifespan is short.

[0009] CN113201839A discloses a polyphenylene sulfide (PPS) fabric for water electrolysis cells. After fabricating the PPS yarn, it undergoes sulfonation treatment at different stages using 300-1000 g / L sulfuric acid and 150-500 g / L chromic acid, followed by washing to obtain the PPS fabric for water electrolysis cells. This patented treatment results in hydrophilic groups on both the surface and interior of the PPS fabric. Even after long-term use, a large number of hydrophilic groups remain, improving the stability and lifespan of the PPS membrane. The mechanism is that chromic acid decomposes the large PPS molecular chains into smaller molecular chains, and concentrated sulfuric acid can penetrate into the PPS for sulfonation, thereby introducing sulfoxy groups onto both the surface and interior of the PPS fibers. However, the strong oxidizing chromic acid in the mixed solution decomposes the large PPS molecular chains into several smaller molecular chains, altering the original physicochemical properties of PPS and reducing the mechanical strength of the PPS membrane.

[0010] Therefore, for PPS membranes used in alkaline water electrolysis for hydrogen production, it is necessary to modify them to be hydrophilic while maintaining their hydrophilicity, being able to withstand high-temperature alkaline electrolysis conditions, and meeting mechanical performance standards. There is also an urgent need to develop a PPS membrane with excellent comprehensive performance that can meet the requirements of alkaline water electrolysis for hydrogen production in actual industrial applications. Summary of the Invention

[0011] To address the short lifespan of hydrophilically modified polyphenylene sulfide (PPS) diaphragm fabrics due to their inability to withstand high-temperature alkaline water electrolysis for extended periods, this invention provides a hydrophilic modification method for PPS woven diaphragm fabrics. This method improves the hydrophilicity of PPS woven diaphragm fabrics, reduces their internal resistance in electrolyzers, and enables them to withstand high-temperature alkaline water electrolysis conditions, allowing them to function effectively for extended periods and meet practical industrial requirements.

[0012] The present invention achieves the above objectives through the following technical solutions:

[0013] A method for preparing a polyphenylene sulfide alkaline water electrolysis membrane includes the following steps:

[0014] (1) The polyphenylene sulfide woven diaphragm cloth was washed and dried in deionized water and ethanol respectively;

[0015] (2) Soak the polyphenylene sulfide woven diaphragm cloth obtained in step (1) in a haloalkane solvent, take it out and dry it for later use;

[0016] (3) The polyphenylene sulfide woven diaphragm cloth obtained in step (2) is soaked in a good organic solvent of polyphenylene sulfide under ultrasonic conditions.

[0017] (4) The impregnated polyphenylene sulfide woven diaphragm cloth obtained in step (3) is subjected to sulfonation reaction, washed and dried to obtain hydrophilic modified PPS alkaline electrolytic water diaphragm.

[0018] Further, in step (1), the thickness of the polyphenylene sulfide woven diaphragm fabric is 0.6-1.0 mm, preferably 0.7-0.8 mm, and the basis weight is 400-500 g / m². 2 The polyphenylene sulfide fiber has a diameter of 7-20 μm, preferably 10-15 μm; it is washed with deionized water and ethanol to remove water-soluble and organic impurities from the PPS woven diaphragm fabric.

[0019] Further, in step (2), the halogenated hydrocarbon is selected from at least one of 1,2-dichloroethane, dichloromethane, trichloromethane, tetrachloromethane, and dichlorobenzene, preferably 1,2-dichloroethane; the purpose of impregnating with the halogenated hydrocarbon is to allow the PPS woven diaphragm fabric to better contact with concentrated sulfuric acid, making its sulfonation more uniform; among them, 1,2-dichloroethane has the best effect. The impregnation time in the halogenated hydrocarbon solvent is 0.5-1 h. There is no particular limitation on the amount of halogenated hydrocarbon solvent used, as long as it can fully impregnate the polyphenylene sulfide woven diaphragm fabric.

[0020] Further, in step (3), the ultrasonic frequency is 30-60 kHz, the soaking time under ultrasonic conditions is 1-3 min, and the good solvent is selected from at least one of amide solvents and imidazolidinone solvents; the amide solvent is selected from at least one of dimethylacetamide and dimethylformamide, and the imidazolidinone is 1,3-dimethyl-2-imidazolidinone. The applicant unexpectedly discovered that impregnating the polyphenylene sulfide woven diaphragm cloth with haloalkanes first, and then impregnating it briefly with a good solvent of polyphenylene sulfide under ultrasonic conditions, can greatly improve the sulfonation modification effect of the PPS woven diaphragm cloth. Not only is the hydrophilicity of the PPS woven diaphragm cloth improved, but it can also withstand alkaline water electrolysis conditions and maintain good hydrophilicity for a long time, making the service life of the polyphenylene sulfide woven diaphragm cloth as an alkaline water electrolysis diaphragm longer. This allows PPS diaphragm materials to play a greater role in the field of water electrolysis in industry, possessing significant industrial advantages and practical significance. The ultrasonic immersion time should not be too long, otherwise the membrane structure will be damaged, reducing the mechanical properties and dimensional stability of the PPS membrane, and also negatively impacting its lifespan in alkaline electrolyzed water. This invention utilizes ultrasonic conditions to shorten the time required for full immersion; an immersion time of 1-3 minutes is preferable.

[0021] Furthermore, the organic solvent is a mixture of amide solvents and imidazolidinone solvents in a volume ratio of 3-5:1. For example, it could be a mixture of dimethylacetamide and 1,3-dimethyl-2-imidazolidinone in a volume ratio of 3-5:1, or a mixture of dimethylformamide and 1,3-dimethyl-2-imidazolidinone in a volume ratio of 3-5:1. Using the above-mentioned compounded solvent system for ultrasonic impregnation achieves the best sulfonation effect.

[0022] Further, in step (4), after the polyphenylene sulfide woven diaphragm cloth is immersed in a good solvent under ultrasonic conditions, it is taken out and directly subjected to sulfonation reaction without drying treatment; the sulfonation reaction is to react the impregnated polyphenylene sulfide woven diaphragm cloth with a sulfonating agent, which is selected from at least one of concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, and sulfur trioxide; there is no particular limitation on the amount of sulfonating agent used, as long as it can impregnate the polyphenylene sulfide woven diaphragm cloth; the sulfonation reaction temperature is 40-50℃, and the reaction time is 30-60min. Since the polyphenylene sulfide woven diaphragm cloth is impregnated with haloalkanes and organic good solvents in steps (2) and (3) respectively, the sulfonation reaction in step (4) proceeds smoothly, and not only the surface of the polyphenylene sulfide woven diaphragm cloth is subjected to sulfonation reaction, but also a certain degree of sulfonation reaction exists inside it.

[0023] Further, in step (4), the washing process consists of ultrasonic water washing, 1,2-dichloroethane washing, and acetone washing in sequence.

[0024] Furthermore, the polyphenylene sulfide woven diaphragm fabric prepared according to the above method has a water absorption rate of less than 10 s, for example, 1-7 s; and a sheet resistivity of 0.25-0.34 Ω·cm. 2 .

[0025] The technical solution of the present invention provides the following beneficial effects:

[0026] (1) This invention involves a two-step impregnation treatment of polyphenylene sulfide woven membrane fabric, namely a long-term pre-impregnation with haloalkanes and a short-term impregnation with a good polyphenylene sulfide solvent under ultrasonic conditions, followed by a sulfonation reaction. This introduces -SO3H onto the benzene ring of the polyphenylene sulfide woven membrane fabric, improving the hydrophilicity of the PPS membrane and reducing its surface resistance as a membrane for alkaline water electrolysis. Moreover, the surface resistance remains stable even after long-term immersion in a high-temperature alkaline electrolyte environment, providing the possibility for large-scale industrial production of hydrogen through water electrolysis under alkaline conditions.

[0027] (2) The hydrophilic modified PPS woven diaphragm cloth of the present invention has good hydrophilicity, which can reduce its surface resistance, reduce energy loss and reduce hydrogen production cost during use. In addition, due to the good hydrophilicity of the diaphragm, a water film can be formed on the surface of the diaphragm during use, which reduces the pore size of the diaphragm and effectively prevents the hydrogen and oxygen generated from passing through each other, thereby increasing the purity of hydrogen and oxygen. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope (SEM) image of a polyphenylene sulfide woven fabric diaphragm.

[0029] Figure 2Photograph of water dripping onto a woven polyphenylene sulfide diaphragm before sulfonation.

[0030] Figure 3 This is a photograph of water dripping from the sulfonated polyphenylene sulfide woven fabric diaphragm of Example 1.

[0031] Figure 4 XPS spectra of sulfur in polyphenylene sulfide woven fabric diaphragms before and after sulfonation. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. The following embodiments are provided to better understand this invention, but do not limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0033] The polyphenylene sulfide (PPS) woven diaphragm fabric was purchased from Zhejiang Zhengben New Material Co., Ltd. The PPS woven diaphragm fabric has a thickness of 0.76 mm and a basis weight of 461 g / m³. 2 Its polyphenylene sulfide fiber diameter is 10-15μm.

[0034] Example 1

[0035] (1) The newly added 10cm×10cm polyphenylene sulfide woven membrane cloth was first washed with deionized water for 30 minutes, then washed with ethanol for 30 minutes, and then dried.

[0036] (2) Soak the dried polyphenylene sulfide woven membrane cloth in 1,2-dichloroethane for 0.5 hours, then take it out and dry it for later use.

[0037] (3) The dried polyphenylene sulfide woven diaphragm cloth obtained in step (2) is immersed in dimethylformamide under 60kHz ultrasonic conditions for 1 minute, and then taken out.

[0038] (4) The polyphenylene sulfide woven diaphragm cloth impregnated in step (3) was reacted with concentrated sulfuric acid at 40°C for 0.5 h. Then the diaphragm cloth was taken out and washed sequentially with deionized water by ultrasonication (30 kHz) for 10 min, 1,2-dichloroethane for 10 min, and finally acetone for 10 min. After washing, it was dried to obtain the hydrophilic modified polyphenylene sulfide woven diaphragm cloth.

[0039] Figure 1 This is a scanning electron microscope (SEM) image of a polyphenylene sulfide woven fabric diaphragm before sulfonation, which shows that the fiber diameter is 7-20 μm. Figure 2 Photograph of water dripping onto a woven polyphenylene sulfide diaphragm before sulfonation. Figure 3 This is a photograph of water droplets from the sulfonated polyphenylene sulfide woven fabric diaphragm of Example 1. It can be seen that the hydrophilicity of the sulfonated polyphenylene sulfide woven fabric diaphragm is significantly improved.

[0040] Example 2

[0041] The other conditions and operations are the same as in Example 1, except that in step (3), the soaking time is 2 minutes.

[0042] Example 3

[0043] The other conditions and operations are the same as in Example 1, except that in step (3), the soaking time is 3 minutes.

[0044] Example 4

[0045] The other conditions and operations are the same as in Example 1, except that in step (3), the soaking time is 4 minutes.

[0046] Example 5

[0047] The other conditions and operations are the same as in Example 2, except that in step (3), the solvent for soaking is 1,3-dimethyl-2-imidazolone.

[0048] Example 6

[0049] The other conditions and operations are the same as in Example 2, except that in step (3), the solvent for soaking is a mixture of dimethylformamide and 1,3-dimethyl-2-imidazolidine ketone in a volume ratio of 3:1.

[0050] Example 7

[0051] The other conditions and operations are the same as in Example 2, except that in step (3), the solvent for soaking is a mixture of dimethylacetamide and 1,3-dimethyl-2-imidazolium ketone in a volume ratio of 5:1.

[0052] Comparative Example 1

[0053] The other conditions and operations are the same as in Example 2, except that step (3) is omitted, and the polyphenylene sulfide woven diaphragm cloth impregnated in 1,2-dichloroethane in step (2) is directly subjected to the sulfonation reaction and post-treatment (washing, drying) in step (4).

[0054] Comparative Example 2

[0055] The other conditions and operations are the same as in Example 2, except that in step (3), the ultrasound condition is cancelled.

[0056] Comparative Example 3

[0057] Other conditions and operations are the same as in Example 2, except that step (2) is omitted and the polyphenylene sulfide woven diaphragm cloth pretreated in step (1) is directly impregnated under ultrasonic conditions with PPS good solvent in step (3).

[0058] Example of effect

[0059] The polyphenylene sulfide woven diaphragm fabrics of the above embodiments and comparative examples were subjected to performance tests. The test items and methods are as follows:

[0060] Morphology and structure: PPS membrane fibers were bonded only to conductive adhesive, and their morphology was characterized using scanning electron microscopy.

[0061] X-ray photoelectron spectroscopy (XPS): The elemental distribution on the surface of the PPS membrane before and after sulfonation was analyzed using an X-ray photoelectron spectroscopy instrument. Samples were cut into 0.5cm × 0.5cm pieces and fixed to a metal plate with conductive tape for testing. The peaks on the unsulfonated PPS membrane corresponded to electron binding energies of 163.3 eV and 164.5 eV, corresponding to the binding energy of the sulfur atom in the sulfoether group on the PPS benzene ring. The sulfonated PPS membrane showed a distinct peak at 169.1 eV, corresponding to the binding energy of the sulfur atom in the sulfonic acid group. This indicates that sulfonic acid groups (-SO3H) were successfully grafted onto the surface of the PPS membrane.

[0062] Sheet resistance: According to the People's Republic of China Electronic Industry Standard SJ / T 10171.5-1991 Test standard for sheet resistance of alkaline battery separator, the sheet resistance of the separator is measured in a self-made sheet resistance testing device.

[0063] Water diffusion time: The water absorption rate and water absorption time before and after hydrophilic treatment are tested according to GB / T21655.1-2008 standard.

[0064] Alkali-resistant electrolytic water environment test: The polyphenylene sulfide woven diaphragm fabrics of the above examples and comparative examples were immersed in 30% wt KOH solution at 80℃ for 300h, and the surface resistivity and water droplet diffusion time were tested. The results are shown in Table 1 below.

[0065] Table 1 Performance test results of PPS diaphragm fabric

[0066]

[0067]

[0068] As shown in Table 1, the hydrophilic modified polyphenylene sulfide woven fabric of the present invention, after undergoing two-step impregnation and sulfonation treatment, significantly improves the hydrophilicity of the polyphenylene sulfide woven membrane fabric and reduces its sheet resistance. Furthermore, it can remain stable for a long time in a high-temperature alkaline electrolyte environment, maintaining a low sheet resistance and a fast water diffusion time. In contrast, the hydrophilic modified polyphenylene sulfide woven fabric of the comparative example either has insufficient hydrophilic modification or cannot withstand the high-temperature alkaline electrolysis environment for a long time, resulting in decreased hydrophilicity, energy loss, and increased hydrogen production costs.

Claims

1. A method for preparing a polyphenylene sulfide alkaline electrolytic water separator, characterized by, Comprising the following steps: (1) Washing, drying the polyphenylene sulfide woven separator cloth in deionized water and ethanol in turn; (2) Soaking the polyphenylene sulfide woven separator cloth obtained in step (1) in a halogenated hydrocarbon solvent, and drying after taking out; (3) Soaking the polyphenylene sulfide woven separator cloth obtained in step (2) in a good organic solvent of polyphenylene sulfide under ultrasonic conditions; the ultrasonic frequency is 30-60 kHz, the soaking time under ultrasonic conditions is 1-3 min; the good organic solvent is a mixed solvent of an amide solvent and an imidazolidone solvent in a volume ratio of 3-5:1; the imidazolidone is 1,3-dimethyl-2-imidazolidinone; (4) Carrying out a sulfonation reaction on the soaked polyphenylene sulfide woven separator cloth obtained in step (3), washing, drying, and obtaining a hydrophilically modified PPS alkaline electrolytic water separator.

2. The production method according to claim 1, characterized by, In step (1), the thickness of the polyphenylene sulfide woven separator cloth is 0.6-1.0 mm, and the grammage is 400-500 g / m 2 The diameter of the polyphenylene sulfide fiber is 7-20 um.

3. The preparation method according to claim 2, characterized in that, In step (1), the thickness of the polyphenylene sulfide woven separator cloth is 0.7-0.8 mm, and the diameter of the polyphenylene sulfide fiber is 10-15 μm.

4. The method of claim 1, wherein, In step (2), the halogenated hydrocarbon is selected from at least one of 1,2-dichloroethane, dichloromethane, trichloromethane, tetrachloromethane, and dichlorobenzene; the soaking time in the halogenated hydrocarbon solvent is 0.5-1 h.

5. The preparation method according to claim 4, characterized in that, In step (2), the halogenated hydrocarbon is 1,2-dichloroethane.

6. The method of claim 1, wherein, In step (3), the amide solvent is selected from at least one of dimethylacetamide and dimethylformamide.

7. The preparation method according to claim 1, characterized in that, In step (4), after the polyphenylene sulfide woven separator cloth is soaked in a good solvent under ultrasonic conditions, it is directly subjected to a sulfonation reaction after taking out without drying treatment; the sulfonation reaction is carried out by contacting the soaked polyphenylene sulfide woven separator cloth with a sulfonation reagent, and the sulfonation reagent is selected from at least one of concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, and sulfur trioxide; the sulfonation reaction temperature is 40-50 ℃, and the reaction time is 30-60 min.

8. The method of claim 1, wherein, In step (4), the washing is water washing, 1,2-dichloroethane washing, and acetone washing in turn under ultrasonic conditions.

9. A polyphenylene sulfide alkaline electrolytic water separator prepared by the preparation method of any one of claims 1-8; the water absorption speed of the polyphenylene sulfide woven separator cloth is less than 10 s, and the surface resistance is 0.25-0.34 Ω·cm².

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