A super-hydrophilic, alkali-resistant polyphenylene sulfide diaphragm, preparation method and application thereof

Abstract

The present invention discloses a super-hydrophilic, strong-alkali-resistant polyphenylene sulfide (PPS) membrane, a preparation method, and its application, comprising: a polyphenylene sulfide fiber and a hydrophilic layer of a modified polydopamine polymer, wherein the thickness of the hydrophilic layer is 40-50 nm; after immersion in an alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting liquid is no more than 5°, and the wetting and water absorption time of the PPS membrane and the alkaline wetting liquid is no more than 0.1 s; under an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the gas on the anode side of an alkaline electrolyzer using the PPS membrane is no more than 0.5%, wherein the alkaline wetting liquid and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%. The hydrophilic layer of the modified polydopamine polymer is prepared by a simple process, the alkali-resistant hydrophilicity of the PPS membrane is improved, the hydrophilic performance degradation and instability problems of the existing hydrophilic layer in the alkaline electrolyzer are overcome, and a super-hydrophilic PPS membrane that can be stably used in an alkaline environment is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by electrolysis of water, and in particular relates to a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method and applications thereof. Background Art

[0002] Among existing water electrolysis technologies, alkaline water electrolysis (AWE) is commonly used for industrial hydrogen production due to its stability and durability. During alkaline water electrolysis, a diaphragm is typically placed between the electrodes to effectively separate the hydrogen and oxygen produced by water electrolysis, improve hydrogen purity, and ensure the safety of the electrolysis process. The diaphragm prevents hydrogen and oxygen from mixing in the electrolysis cell, thereby avoiding the risk of explosion and improving product purity.

[0003] In AWE, the diaphragm is typically a porous membrane made of organic or inorganic materials, and is required to possess sufficient strength, toughness, and durability to withstand strong alkaline electrolytes and high temperatures (typically around 80°C). Research on diaphragms in alkaline water electrolysis also focuses on improving their stability and physical properties in chemical environments.

[0004] Furthermore, the diaphragm must be highly hydrophilic to allow the electrolyte to fully fill its porous structure. If the diaphragm's hydrophilicity is poor, the diaphragm cloth will not be fully wetted by the electrolyte, resulting in poor ion permeability and increased diaphragm resistance. This ultimately reduces electrolytic efficiency in the electrolyzer and significantly wastes energy. Insufficient diaphragm hydrophilicity is one of the greatest challenges facing diaphragms.

[0005] Currently, various methods, such as surface modification and composite materials, have been developed to improve the hydrophilicity of diaphragms. For example, patent CN118198649A discloses a method for preparing a diaphragm, a diaphragm, and a battery therefor, comprising the following steps: immersing the diaphragm substrate in a sulfuric acid solution for sulfonation to obtain a sulfonated diaphragm; immersing the sulfonated diaphragm in a dopamine solution to form a polydopamine coating on the diaphragm surface; and drying the diaphragm. The dopamine solution contains sodium borate and dopamine hydrochloride. The method also provides a diaphragm and a battery therefor. The diaphragm provided by this method has a simple synthesis process. The diaphragm is sulfonated to graft hydrophilic functional groups, such as sulfate groups, onto its surface. The sulfonated diaphragm is then immersed in a dopamine solution, which has a rich variety of functional groups, such as -OH and -NH-, which significantly improves the hydrophilicity and liquid retention of the diaphragm.

[0006] Polyphenylene sulfide (PPS) membranes offer excellent heat resistance, high mechanical strength, and good electrical properties, making them a commonly used commercial alkaline electrolyzer membrane material. However, PPS membranes have poor hydrophilicity. Introducing a hydrophilic coating on the surface of the PPS membrane can improve hydrophilicity and ion permeability. For example, patent CN117904870A discloses a PPS fabric for alkaline water electrolysis and its preparation method. The PPS fabric is obtained by sequentially granulating, drying, melt-spinning, weaving, and braiding the PPS resin. Dopamine hydrochloride and a Tris-HCl buffer solution are then used as raw materials to obtain a mixed solution. The PPS fabric is immersed in the mixed solution, forming a polydopamine layer on the surface of the PPS fabric. The PPS fabric is then immersed in a reaction solution 1 containing mercaptoethylamine as the primary raw material, and a reaction solution 2 containing sulfonic acids and acrylic acid as the primary raw materials, to obtain the finished product. The polyphenylene sulfide fabric obtained by this solution has good hydrophilicity and chemical resistance, and therefore has broad application prospects in the field of membrane preparation technology.

[0007] However, the above existing technologies have limited effect on improving the hydrophilicity of the membrane. The introduced polydopamine coating will aggregate in the alkaline environment of the alkaline electrolyzer for a long time, causing clogging of the membrane pores of the polydopamine coating, affecting the hydrophilicity and ion permeability of the membrane.

[0008] Therefore, how to improve the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane and overcome the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in the alkaline electrolytic cell environment to obtain a super hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0009] In response to the defects in the above-mentioned prior art, the present invention provides a super hydrophilic and alkali-resistant polyphenylene sulfide membrane, a preparation method and its application. The polyphenylene sulfide membrane specifically includes: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50 nm; the water contact angle between the polyphenylene sulfide membrane and the alkaline wetting liquid is not greater than 5°, and the wetting and water absorption time of the polyphenylene sulfide membrane and the alkaline wetting liquid is not greater than 0.1 s; under an operating voltage of 1.8 V and an alkaline electrolyte, the hydrogen content in the anode side gas of the alkaline electrolytic cell using the polyphenylene sulfide membrane is not higher than 0.5%, wherein the alkaline wetting liquid and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%. The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, improves the alkali resistance and hydrophilicity of a polyphenylene sulfide membrane, overcomes the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and prepares a super-hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment.

[0010] In a first aspect, the present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, specifically comprising: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber or sulfonated polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50 nm;

[0011] The polyphenylene sulfide diaphragm is immersed in an alkaline electrolyte for 120 hours, and the water contact angle with the alkaline wetting liquid is not greater than 5°. The wetting and water absorption time of the polyphenylene sulfide diaphragm with the alkaline wetting liquid is not greater than 0.1s;

[0012] Under an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolytic cell using a polyphenylene sulfide diaphragm is no more than 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%.

[0013] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane is a polyphenylene sulfide membrane having a water contact angle with an alkaline wetting liquid of no more than 5°.

[0014] In alkaline electrolytic cells, oxygen is produced on the anode side and hydrogen on the cathode side. The function of the diaphragm is to prevent the mixing of hydrogen produced at the cathode and oxygen produced at the anode. The super-hydrophilic, strong-alkali-resistant polyphenylene sulfide diaphragm of the present invention allows electrolyte ions to pass through, preventing hydrogen and oxygen from mixing. The hydrogen content in the gas produced on the anode side is no more than 0.5%.

[0015] Furthermore, the most probable pore size of the hydrophilic layer is not greater than 40 μm. The most probable pore size is the pore size value of the peak on the pore size differential distribution curve.

[0016] Furthermore, the elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is 0.8-1.2.

[0017] In a second aspect, the present invention further provides a method for preparing the above-mentioned super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, which specifically comprises the following steps:

[0018] Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane;

[0019] Step S2: The pretreated polyphenylene sulfide membrane of step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with a modified polydopamine polymer attached thereto, and after cleaning and drying, a super hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained, wherein the mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is (1-2):1, the concentration of dopamine is 2-3 mg / ml, and the weight-average molecular weight of polyethyleneimine is not higher than 600.

[0020] Furthermore, step S1 specifically includes:

[0021] Step S11: placing a base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold, preheating the chamber, turning on the high-voltage power supply, setting the discharge frequency to 40-50 kHz, and performing plasma treatment for 5-10 minutes before turning off the power supply;

[0022] Step S12: turning over the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers, and repeating step S11;

[0023] Step S13: repeating steps S11 and S12 until the water absorption time of the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers is no more than 0.5 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

[0024] Furthermore, in step S1, the threshold of the vacuum degree is 20-50 Pa, and the preheating temperature is not higher than 50°C.

[0025] When the vacuum reaches the threshold and preheating occurs, a small amount of air flows back into the plasma treatment chamber, and the high-voltage power supply excites oxygen into ions. Plasma surface treatment improves the hydrophilicity of polyphenylene sulfide fibers, introduces oxygen-containing polar functional groups (e.g., -OH) on the surface of the base film, and forms multiple active sites. It also creates a microscopic roughness that serves as an ideal substrate for the polydopamine layer to adhere.

[0026] Furthermore, in step S2, the mixed aqueous solution also includes tris(hydroxymethyl)aminomethane, polyethylene polyamine and a phosphate mixture, and the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is (20-25):1, the concentration of polyethylene polyamine is 8-15 mg / ml, and the pH of the mixed aqueous solution is 8.5-8.8, wherein the phosphate mixture includes dipotassium hydrogen phosphate and potassium dihydrogen phosphate.

[0027] Furthermore, the polyethylene polyamine is a co-product of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. The ratio of the various components of the polyethylene polyamine can be adjusted according to the specific application scenario. In addition, the ratio of dipotassium hydrogen phosphate to potassium dihydrogen phosphate in the phosphate mixture can also be adjusted according to the specific application scenario.

[0028] Furthermore, in step S2, the preparation of the mixed aqueous solution specifically includes:

[0029] A Tris solution and a phosphate buffer solution are prepared using a mixture of Tris and a phosphate, and the Tris solution and the phosphate buffer solution are mixed according to a molar ratio to form an initial mixed aqueous solution, wherein the concentration of the Tris solution is 50-60 mmol / L;

[0030] Dopamine powder, polyethyleneimine and polyethylene polyamine are added into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution.

[0031] Dopamine and polyethyleneimine (low weight-average molecular weight) co-deposit onto the surface of a pretreated polyphenylene sulfide (PPS) separator. The polyethyleneimine undergoes Michael addition, accelerating copolymerization with dopamine and reducing dopamine self-aggregation. This enhances the stability of the polymerization, preventing the formation of aggregates caused by dopamine self-aggregation in long-term alkaline environments. The addition of polyethyleneimine during the co-deposition of dopamine and polyethyleneimine improves the uniformity and adhesion of the hydrophilic coating.

[0032] In addition, the pH value of the mixed aqueous solution is adjusted by using tris(hydroxymethyl)aminomethane solution and phosphate buffer solution to promote the polymerization of dopamine and polyethyleneimine.

[0033] Furthermore, in step S2, the soaking modification treatment specifically includes:

[0034] The temperature of the mixed aqueous solution is 20-30°C, and the pretreated polyphenylene sulfide membrane in step S1 is immersed in the mixed aqueous solution for modification for 12-48 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is not less than 1 / 20L0 / min, where L0 is the volume of the mixed aqueous solution.

[0035] During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating.

[0036] In a third aspect, the present invention further provides an application of a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is applied to an alkaline water electrolysis hydrogen production tank.

[0037] The present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method, and applications thereof, which have at least the following beneficial effects:

[0038] (1) The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, thereby improving the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane, overcoming the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and preparing a super-hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment.

[0039] (2) Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the polyphenylene sulfide fiber base membrane, form multiple active points, and also produce a microscopic rough structure that is a good substrate for the attachment of the polydopamine layer.

[0040] (3) Dopamine and polyethyleneimine (with a low weight-average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide membrane. Polyethyleneimine undergoes Michael addition, which accelerates copolymerization with dopamine, reduces dopamine self-polymerization, and enhances the stability of the polymerization, thus avoiding the formation of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are co-deposited, the addition of polyethyleneimine can improve the uniformity and adhesion of the hydrophilic coating.

[0041] (4) During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Surface SEM images of the polyphenylene sulfide membrane of Example 1 provided by the present invention before and after the alkali resistance test;

[0043] Figure 2 This is an example diagram of the water contact angle of the polyphenylene sulfide membrane of Example 1 provided by the present invention;

[0044] Figure 3 This is an example diagram of the water contact angle of the polyphenylene sulfide membrane of Example 2 provided by the present invention;

[0045] Figure 4 This is an example diagram of the water contact angle of the polyphenylene sulfide membrane of Comparative Example 5 provided by the present invention. DETAILED DESCRIPTION

[0046] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0048] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0049] Existing technologies have limited effectiveness in improving the hydrophilicity of the membrane. The introduced polydopamine coating forms aggregates in the alkaline environment of an alkaline electrolyzer over a long period of time, causing clogging of the membrane pores and affecting the membrane's hydrophilicity and ion permeability.

[0050] At present, there is still a need to improve the alkali resistance and hydrophilicity of polyphenylene sulfide membranes, overcome the problems of hydrophilic performance degradation and instability of the existing hydrophilic layer in the alkaline electrolytic cell environment, and obtain a super-hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment.

[0051] In a first aspect, the present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, specifically comprising: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber or sulfonated polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50 nm;

[0052] The polyphenylene sulfide diaphragm is immersed in an alkaline electrolyte for 120 hours, and the water contact angle with the alkaline wetting liquid is not greater than 5°. The wetting and water absorption time of the polyphenylene sulfide diaphragm with the alkaline wetting liquid is not greater than 0.1s;

[0053] Under an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolytic cell using a polyphenylene sulfide diaphragm is no more than 0.5%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%-50%.

[0054] The super hydrophilic and alkali-resistant polyphenylene sulfide membrane is a polyphenylene sulfide membrane having a water contact angle with an alkaline wetting liquid of no more than 5°.

[0055] Furthermore, the most probable pore size of the hydrophilic layer is not greater than 40 μm. The most probable pore size is the pore size value of the peak on the pore size differential distribution curve.

[0056] Furthermore, the elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is 0.8-1.2.

[0057] In a second aspect, the present invention further provides a method for preparing the above-mentioned super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, which specifically comprises the following steps:

[0058] Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane;

[0059] Step S2: The pretreated polyphenylene sulfide membrane of step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with a modified polydopamine polymer attached thereto, and after cleaning and drying, a super hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained, wherein the mixed aqueous solution includes dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is (1-2):1, the concentration of dopamine is 2-3 mg / ml, and the weight-average molecular weight of polyethyleneimine is not higher than 600.

[0060] Furthermore, step S1 specifically includes:

[0061] Step S11: placing a base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold, preheating the chamber, turning on the high-voltage power supply, setting the discharge frequency to 40-50 kHz, and performing plasma treatment for 5-10 minutes before turning off the power supply;

[0062] Step S12: turning over the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers, and repeating step S11;

[0063] Step S13: repeating steps S11 and S12 until the water absorption time of the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers is no more than 0.5 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

[0064] Furthermore, in step S1, the threshold of the vacuum degree is 20-50 Pa, and the preheating temperature is not higher than 50°C.

[0065] Furthermore, in step S2, the mixed aqueous solution also includes tris(hydroxymethyl)aminomethane, polyethylene polyamine and a phosphate mixture, and the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is (20-25):1, the concentration of polyethylene polyamine is 8-15 mg / ml, and the pH of the mixed aqueous solution is 8.5-8.8, wherein the phosphate mixture includes dipotassium hydrogen phosphate and potassium dihydrogen phosphate.

[0066] Furthermore, the polyethylene polyamine is a co-product of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. The ratio of the various components of the polyethylene polyamine can be adjusted according to the specific application scenario. In addition, the ratio of dipotassium hydrogen phosphate to potassium dihydrogen phosphate in the phosphate mixture can also be adjusted according to the specific application scenario.

[0067] Furthermore, in step S2, the preparation of the mixed aqueous solution specifically includes:

[0068] A Tris solution and a phosphate buffer solution are prepared using a mixture of Tris and a phosphate, and the Tris solution and the phosphate buffer solution are mixed according to a molar ratio to form an initial mixed aqueous solution, wherein the concentration of the Tris solution is 50-60 mmol / L;

[0069] Dopamine powder, polyethyleneimine and polyethylene polyamine are added into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution.

[0070] Furthermore, in step S2, the soaking modification treatment specifically includes:

[0071] The temperature of the mixed aqueous solution is 20-30°C, and the pretreated polyphenylene sulfide membrane in step S1 is immersed in the mixed aqueous solution for modification for 12-48 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is not less than 1 / 20L0 / min, where L0 is the volume of the mixed aqueous solution.

[0072] In a third aspect, the present invention further provides an application of a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is applied to an alkaline water electrolysis hydrogen production tank.

[0073] The present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method, and applications thereof, which have at least the following beneficial effects:

[0074] (1) The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, thereby improving the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane, overcoming the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and preparing a super-hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment.

[0075] (2) Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the polyphenylene sulfide fiber base membrane, form multiple active points, and also produce a microscopic rough structure that is a good substrate for the attachment of the polydopamine layer.

[0076] (3) Dopamine and polyethyleneimine (with a low weight-average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide membrane. Polyethyleneimine undergoes Michael addition, which accelerates copolymerization with dopamine, reduces dopamine self-polymerization, and enhances the stability of the polymerization, thus avoiding the formation of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are co-deposited, the addition of polyethyleneimine can improve the uniformity and adhesion of the hydrophilic coating.

[0077] (4) During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating.

[0078] Example 1:

[0079] In Example 1, the specific steps for preparing the super hydrophilic and alkali-resistant polyphenylene sulfide membrane are as follows:

[0080] Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane;

[0081] Among them, step S1 specifically includes: step S11: placing a base film woven from polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold value (the threshold value is a preset value, which is 40 Pa in this embodiment 1), preheating (the preheating temperature is 30° C.), turning on the high-voltage power supply, setting the discharge frequency to 45 kHz, and plasma treating for 5 minutes, and then turning off the power supply;

[0082] Step S12: turning over the base film woven from polyphenylene sulfide fibers and repeating step S11;

[0083] Step S13: Repeat step S11 and step S12 again, and test to obtain that the water absorption time of the base membrane woven with polyphenylene sulfide fibers is 0.4 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

[0084] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with attached modified polydopamine polymer. After washing and drying, a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0085] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, and adding 1 L of deionized water to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine in a mass ratio of 1:1, a dopamine concentration of 2 mg / ml, and a polyethyleneimine weight-average molecular weight of approximately 550.

[0086] Soaking modification treatment, specifically including:

[0087] The temperature of the mixed aqueous solution is 25° C. The pretreated polyphenylene sulfide membrane obtained in step S1 is immersed in the mixed aqueous solution for modification for 30 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is maintained at 50 ml / min.

[0088] The super hydrophilic alkali-resistant polyphenylene sulfide membrane prepared by the above steps (such as Figure 1 As shown), specifically comprising: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40 nm;

[0089] The polyphenylene sulfide membrane was immersed in alkaline electrolyte for 120 h (such as Figure 1 As shown), the contact angle with alkaline wetting fluid is close to 0° (as shown Figure 2 As shown), the wetting and water absorption time of the polyphenylene sulfide membrane and the alkaline wetting liquid is about 0.05s;

[0090] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.3%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% KOH solutions by mass.

[0091] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 38 μm.

[0092] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0093] Example 2:

[0094] Based on Example 1, Example 2 adjusts the following parameters.

[0095] Compared with the preparation process of Example 1, step S2 of this embodiment is specifically adjusted as follows:

[0096] The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto. After washing and drying, a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0097] The pre-prepared mixed aqueous solution specifically includes:

[0098] A Tris solution and a phosphate buffer solution were prepared using a mixture of Tris and a phosphate, and the Tris solution and the phosphate buffer solution were mixed according to a molar ratio to form an initial mixed aqueous solution, wherein the concentration of the Tris solution was 50 mmol / L;

[0099] Adding dopamine powder, polyethyleneimine and polyethylene polyamine into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution;

[0100] In the mixed aqueous solution, the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is about 20:1, the concentration of polyethylene polyamine is 10 mg / ml, and the pH of the mixed aqueous solution is about 8.5.

[0101] In this embodiment, the polyethylene polyamine is a co-product of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, and the molar ratio of each component is about 1:1:1:1. The molar ratio of dipotassium hydrogen phosphate to potassium dihydrogen phosphate in the phosphate mixture is about 1:1.

[0102] In the mixed aqueous solution, the mass ratio of dopamine to polyethyleneimine is 1:1, the concentration of dopamine is 2 mg / ml, and the weight average molecular weight of polyethyleneimine is about 550.

[0103] Soaking modification treatment, specifically including:

[0104] The temperature of the mixed aqueous solution is 25° C. The pretreated polyphenylene sulfide membrane obtained in step S1 is immersed in the mixed aqueous solution for modification for 30 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is maintained at 50 ml / min.

[0105] The super-hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 42 nm;

[0106] The polyphenylene sulfide membrane was immersed in alkaline electrolyte for 120h, and the water contact angle with the alkaline wetting solution was close to 0°. The wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution was about 0.02s (e.g. Figure 3 shown);

[0107] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.1%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% by mass KOH solutions.

[0108] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 35 μm.

[0109] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0110] Example 3:

[0111] Based on Example 1, Example 3 adjusts the following parameters.

[0112] Compared with the preparation process of Example 1, step S2 of this embodiment is specifically adjusted as follows:

[0113] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with attached modified polydopamine polymer. After washing and drying, a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0114] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, and adding 1 L of deionized water to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine in a mass ratio of 2:1, a dopamine concentration of 2 mg / ml, and a polyethyleneimine weight-average molecular weight of approximately 550.

[0115] The super-hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 45 nm;

[0116] When the polyphenylene sulfide membrane is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 0°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution is about 0.08s;

[0117] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.3%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% KOH solutions by mass.

[0118] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0119] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0120] Example 4:

[0121] Based on Example 1, Example 4 adjusts the following parameters.

[0122] Compared with the preparation process of Example 1, step S2 of this embodiment is specifically adjusted as follows:

[0123] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with attached modified polydopamine polymer. After washing and drying, a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane is obtained.

[0124] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, and adding 1 L of deionized water to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine in a mass ratio of 1:1, a dopamine concentration of 3 mg / ml, and a polyethyleneimine weight-average molecular weight of approximately 550.

[0125] The super-hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 45 nm;

[0126] When the polyphenylene sulfide membrane is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 0°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution is about 0.08s;

[0127] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.3%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% KOH solutions by mass.

[0128] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0129] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0130] Example 5:

[0131] Based on Example 2, Example 5 adjusts the following parameters.

[0132] Compared with the preparation process of Example 2, step S2 of this embodiment is specifically adjusted as follows:

[0133] A pre-prepared mixed aqueous solution comprising:

[0134] A Tris solution and a phosphate buffer solution were prepared using a mixture of Tris and a phosphate, and the Tris solution and the phosphate buffer solution were mixed according to a molar ratio to form an initial mixed aqueous solution, wherein the concentration of the Tris solution was 60 mmol / L;

[0135] Adding dopamine powder, polyethyleneimine and polyethylene polyamine into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution;

[0136] In the mixed aqueous solution, the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is about 25:1, and the pH of the mixed aqueous solution is about 8.8.

[0137] The super-hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40 nm;

[0138] When the polyphenylene sulfide membrane is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 0°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution is about 0.06s;

[0139] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.3%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% KOH solutions by mass.

[0140] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 37 μm.

[0141] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0142] Comparative Example 1:

[0143] On the basis of Example 1, the following parameters were adjusted in Comparative Example 1.

[0144] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0145] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with attached polydopamine polymer, and after washing and drying, a polyphenylene sulfide membrane is obtained.

[0146] The pre-prepared mixed aqueous solution specifically comprises: adding dopamine powder to 1L of deionized water according to a mass ratio to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine at a concentration of 2mg / ml.

[0147] Soaking modification treatment, specifically including:

[0148] The temperature of the mixed aqueous solution is 25° C. The pretreated polyphenylene sulfide membrane obtained in step S1 is immersed in the mixed aqueous solution for modification for 30 hours. During the immersion modification process, oxygen is continuously introduced into the mixed aqueous solution, and the oxygen flow rate is maintained at 50 ml / min.

[0149] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is polydopamine polymer, and the thickness of the hydrophilic layer is 40 nm;

[0150] When the polyphenylene sulfide membrane is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 20°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution is about 0.5s;

[0151] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.5%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% by mass KOH solutions.

[0152] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0153] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0154] Comparative Example 2:

[0155] This comparative example uses the polyphenylene sulfide fabric for alkaline water electrolysis prepared in Example 1 of patent CN117904870A.

[0156] Comparative Example 3:

[0157] On the basis of Example 1, the following parameters were adjusted in Comparative Example 3.

[0158] Compared with the preparation process of Example 1, step S1 is omitted in this comparative example.

[0159] The polyphenylene sulfide separator prepared by the above steps specifically includes: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0160] When the polyphenylene sulfide separator is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 136°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution is greater than 10 seconds;

[0161] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.5%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% by mass KOH solutions.

[0162] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0163] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0164] Comparative Example 4:

[0165] On the basis of Example 1, the following parameters were adjusted in Comparative Example 4.

[0166] Compared with the preparation process of Example 1, step S1 of this comparative example is specifically adjusted as follows:

[0167] Step S1 specifically includes: Step S11: placing a base film woven from polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold value (the threshold value is a preset value, which is 40 Pa in Example 1), preheating (the preheating temperature is 30° C.), turning on the high-voltage power supply, setting the discharge frequency to 45 kHz, and performing plasma treatment for 20 minutes, then turning off the power supply;

[0168] Step S12: turning over the base film woven from polyphenylene sulfide fibers and repeating step S11;

[0169] Step S13: obtaining a pretreated polyphenylene sulfide membrane.

[0170] The polyphenylene sulfide separator prepared by the above steps specifically includes: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0171] When the polyphenylene sulfide membrane is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 20°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution is about 0.5s;

[0172] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.8%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% by mass KOH solutions.

[0173] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 40 μm.

[0174] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was approximately 1.

[0175] Comparative Example 5:

[0176] On the basis of Example 1, the following parameters were adjusted in Comparative Example 5.

[0177] Compared with the preparation process of Example 1, step S2 is omitted in this comparative example.

[0178] The polyphenylene sulfide separator prepared by the above steps specifically comprises: a base film, which is polyphenylene sulfide fiber that has been subjected to plasma surface treatment;

[0179] The polyphenylene sulfide separator was immersed in alkaline electrolyte for 120 h, and the contact angle with alkaline wetting solution was close to 136° (e.g. Figure 4 shown);

[0180] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of the alkaline electrolytic cell using a polyphenylene sulfide diaphragm is approximately 0.6%, wherein the alkaline wetting solution and the alkaline electrolyte are both KOH solutions with a mass concentration of 30%.

[0181] Comparative Example 6:

[0182] On the basis of Example 1, the following parameters were adjusted in Comparative Example 6.

[0183] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0184] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto. After washing and drying, a polyphenylene sulfide membrane is obtained.

[0185] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, and adding 1 L of deionized water to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine in a mass ratio of 5:1, a dopamine concentration of 2 mg / ml, and a polyethyleneimine weight-average molecular weight of approximately 550.

[0186] The polyphenylene sulfide separator prepared by the above steps specifically includes: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0187] When the polyphenylene sulfide membrane is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 20°, and the wetting and water absorption time of the polyphenylene sulfide membrane with the alkaline wetting solution is about 0.2s;

[0188] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.5%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% by mass KOH solutions.

[0189] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0190] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0191] Comparative Example 7:

[0192] On the basis of Example 1, the following parameters were adjusted in Comparative Example 7.

[0193] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0194] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto. After washing and drying, a polyphenylene sulfide membrane is obtained.

[0195] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, and adding 1 L of deionized water to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine in a mass ratio of 1:2, a dopamine concentration of 2 mg / ml, and a polyethyleneimine weight-average molecular weight of approximately 550.

[0196] The polyphenylene sulfide separator prepared by the above steps specifically includes: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0197] When the polyphenylene sulfide separator is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 136°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution is greater than 10 seconds;

[0198] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.6%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% by mass KOH solutions.

[0199] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0200] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0201] Comparative Example 8:

[0202] On the basis of Example 1, the following parameters were adjusted in Comparative Example 8.

[0203] Compared with the preparation process of Example 1, step S2 of this comparative example is specifically adjusted as follows:

[0204] Step S2: The pretreated polyphenylene sulfide membrane obtained in step S1 is placed in a pre-prepared mixed aqueous solution for immersion modification to obtain a polyphenylene sulfide membrane with modified polydopamine polymer attached thereto. After washing and drying, a polyphenylene sulfide membrane is obtained.

[0205] The pre-prepared mixed aqueous solution specifically comprises: mixing dopamine powder and polyethyleneimine according to a mass ratio, and adding 1 L of deionized water to prepare a mixed aqueous solution. The mixed aqueous solution includes dopamine and polyethyleneimine in a mass ratio of 1:1, a dopamine concentration of 2 mg / ml, and a polyethyleneimine weight-average molecular weight of approximately 3000.

[0206] The polyphenylene sulfide separator prepared by the above steps specifically includes: a base membrane and a hydrophilic layer, the base membrane is polyphenylene sulfide fiber, the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40nm;

[0207] When the polyphenylene sulfide separator is immersed in alkaline electrolyte for 120 hours, the water contact angle with the alkaline wetting solution is close to 136°, and the wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting solution is greater than 10 seconds;

[0208] At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is approximately 0.7%, wherein both the alkaline wetting solution and the alkaline electrolyte are 30% KOH solutions by mass.

[0209] The most probable pore size of the modified polydopamine polymer as the hydrophilic layer is about 45 μm.

[0210] In addition, the element content of the modified polydopamine polymer as the hydrophilic layer was characterized. The elements of the hydrophilic layer included C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer was about 1.5.

[0211] Testing process:

[0212] Alkali Resistance Test: To verify the alkali resistance of the membranes, the membranes prepared in Examples 1-5 and Comparative Examples 1-8 were cut into 2 cm × 2 cm squares and immersed in a 30% KOH solution at 80°C for 120 hours. Hydrophilicity testing, namely, contact angle testing, was performed. The test used a 30% KOH solution as the alkaline wetting solution. A 5 μL droplet (i.e., a single droplet) was sampled to obtain the contact angle and wetting time.

[0213] Surface resistance test: The surface resistance test refers to SJ / T 10171-2016 "General test method for basic properties of alkaline battery separators", and the test is carried out according to the test item part of section 4.8 area resistance (surface resistance).

[0214] Table 1 Performance comparison of examples and comparative examples

[0215]

[0216]

[0217] The data in Table 1 include the test results obtained from various embodiments and comparative examples of the present invention.

[0218] In particular, the alkali resistance test shows that the water contact angles of the diaphragms in Examples 1-5 are close to 0°, while those in the comparative examples are almost all above 20°. In particular, the water contact angles can even increase to 136° when the plasma surface treatment is lacking in Comparative Example 3, and when the hydrophilic layer is lacking or the polyethyleneimine content does not meet the requirements in Comparative Examples 5, 7, and 8. Similarly, an increase in the water contact angle significantly increases the wetting and water absorption time.

[0219] The super-hydrophilic, strong-alkali-resistant polyphenylene sulfide membrane is a polyphenylene sulfide membrane having a water contact angle of no greater than 5° with the alkaline wetting liquid. The above test results demonstrate that the membranes prepared for use in alkaline hydrolysis tanks in various examples meet the super-hydrophilic requirements and exhibit excellent gas barrier properties.

[0220] The present invention provides a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, a preparation method, and applications thereof, which have at least the following beneficial effects:

[0221] (1) The present invention prepares a hydrophilic layer of a modified polydopamine polymer through a simple process, thereby improving the alkali resistance and hydrophilicity of the polyphenylene sulfide membrane, overcoming the problem of hydrophilic performance degradation and instability of the existing hydrophilic layer in an alkaline electrolytic cell environment, and preparing a super-hydrophilic polyphenylene sulfide membrane that can be used stably in an alkaline environment.

[0222] (2) Plasma surface treatment can improve the hydrophilicity of polyphenylene sulfide fibers, introduce oxygen-containing polar functional groups (e.g., -OH) on the surface of the polyphenylene sulfide fiber base membrane, form multiple active points, and also produce a microscopic rough structure that is a good substrate for the attachment of the polydopamine layer.

[0223] (3) Dopamine and polyethyleneimine (with a low weight-average molecular weight) are co-deposited and attached to the surface of the pretreated polyphenylene sulfide membrane. Polyethyleneimine undergoes Michael addition, which accelerates copolymerization with dopamine, reduces dopamine self-polymerization, and enhances the stability of the polymerization, thus avoiding the formation of aggregates caused by dopamine self-polymerization in a long-term alkaline environment. When dopamine and polyethyleneimine are co-deposited, the addition of polyethyleneimine can improve the uniformity and adhesion of the hydrophilic coating.

[0224] (4) During the modified deposition process, oxygen is introduced into the mixed aqueous solution evenly and slowly, which can not only make the oxygen in the solution evenly distributed and make the deposition of the modified polydopamine polymer more uniform, but also accelerate the copolymerization of dopamine and polyethyleneimine, reduce the deposition time, and improve the deposition quality of the hydrophilic coating.

[0225] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, characterized in that: The polyphenylene sulfide separator specifically includes: a base membrane and a hydrophilic layer, wherein the base membrane is polyphenylene sulfide fiber or sulfonated polyphenylene sulfide fiber, and the hydrophilic layer is a modified polydopamine polymer, and the thickness of the hydrophilic layer is 40-50 nm; The polyphenylene sulfide separator is immersed in an alkaline electrolyte for 120 hours, and the water contact angle with the alkaline wetting liquid is not greater than 5°. The wetting and water absorption time of the polyphenylene sulfide separator with the alkaline wetting liquid is not greater than 0.1 s. At an operating voltage of 1.8V and an alkaline electrolyte, the hydrogen content in the anode-side gas of an alkaline electrolyzer using a polyphenylene sulfide diaphragm is not higher than 0.5%, wherein both the alkaline wetting solution and the alkaline electrolyte are KOH solutions with a mass concentration of 30%-50%; The preparation method specifically comprises the following steps: Step S1: performing plasma surface treatment on a base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers to obtain a pretreated polyphenylene sulfide membrane; Step S2: placing the pretreated polyphenylene sulfide membrane of step S1 in a pre-prepared mixed aqueous solution for immersion modification treatment to obtain a polyphenylene sulfide membrane with a modified polydopamine polymer attached thereto, and after washing and drying, obtaining a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane, wherein the mixed aqueous solution comprises dopamine and polyethyleneimine, the mass ratio of dopamine to polyethyleneimine is (1-2):1, the concentration of dopamine is 2-3 mg / ml, and the weight-average molecular weight of polyethyleneimine is not higher than 600; The mixed aqueous solution also includes tris(hydroxymethyl)aminomethane, polyethylene polyamine and a phosphate mixture, and the molar ratio of tris(hydroxymethyl)aminomethane to the phosphate mixture is (20-25):1, the concentration of polyethylene polyamine is 8-15 mg / ml, and the pH of the mixed aqueous solution is 8.5-8.8, wherein the phosphate mixture includes dipotassium hydrogen phosphate and potassium dihydrogen phosphate.

2. The method for preparing a super-hydrophilic, alkali-resistant polyphenylene sulfide membrane according to claim 1, wherein: The most probable pore size of the hydrophilic layer is no greater than 40 μm.

3. The method for preparing a super-hydrophilic, alkali-resistant polyphenylene sulfide membrane according to claim 2, wherein: The elements of the hydrophilic layer include C, N, and O, wherein the nitrogen-oxygen ratio of the elements in the hydrophilic layer is 0.8-1.

2.

4. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 1, wherein: Step S1 specifically includes: Step S11: placing a base film woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers in a plasma treatment chamber, turning on the power supply, evacuating the chamber until the vacuum reaches a threshold, preheating, turning on the high-voltage power supply, setting the discharge frequency to 40-50 kHz, and performing plasma treatment for 5-10 minutes before turning off the power supply; Step S12: turning over the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers, and repeating step S11; Step S13: repeating steps S11 and S12 until the water absorption time of the base membrane woven from polyphenylene sulfide fibers or sulfonated polyphenylene sulfide fibers is no more than 0.5 s, thereby obtaining a pretreated polyphenylene sulfide membrane.

5. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 4, wherein: In step S1, the threshold of the vacuum degree is 20-50 Pa, and the preheating temperature is not higher than 50°C.

6. The method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane according to claim 1, wherein: In step S2, the preparation of the mixed aqueous solution specifically includes: A Tris solution and a phosphate buffer solution are prepared using a mixture of Tris and a phosphate, and the Tris solution and the phosphate buffer solution are mixed according to a molar ratio to form an initial mixed aqueous solution, wherein the concentration of the Tris solution is 50-60 mmol / L; Dopamine powder, polyethyleneimine and polyethylene polyamine are added into the initial mixed aqueous solution according to the mass ratio to prepare a mixed aqueous solution.

7. An application of a super-hydrophilic and alkali-resistant polyphenylene sulfide diaphragm, characterized in that: The super-hydrophilic and alkali-resistant polyphenylene sulfide membrane prepared by the method for preparing a super-hydrophilic and alkali-resistant polyphenylene sulfide membrane as described in any one of claims 1 to 6 is applied to an alkaline water electrolysis hydrogen production tank.

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