Modified preparation method of PPS diaphragm for hydrogen production by alkaline electrolysis of water

Abstract

The invention discloses a modified preparation method of a PPS diaphragm for hydrogen production by alkaline electrolysis of water. The modified preparation method comprises the steps of pretreatment, dopamine hydrophilic treatment and the like. Through the mode, the PPS diaphragm modification preparation method for hydrogen production by alkaline electrolysis of water effectively improves the hydrophilicity of the PPS diaphragm, optimizes the pore size distribution of the diaphragm, more efficiently plays the roles of gas barrier and ion conduction, and is simple in operation process, relatively low in cost, and suitable for industrial production. And wide application of the PPS diaphragm in a high-performance alkaline water electrolysis hydrogen production system is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragms for hydrogen production, and in particular to a method for modifying and preparing a PPS diaphragm for hydrogen production by alkaline water electrolysis. Background Art

[0002] Against the backdrop of a global energy transition, excessive fossil fuel consumption has not only triggered a severe energy crisis but also brought about a series of environmental problems, including an intensified greenhouse effect and air pollution. Countries around the world are committed to exploring new, sustainable energy systems. Hydrogen, with its zero-carbon emissions, high energy density, and renewable nature, stands out among numerous new energy sources, becoming one of the core forces driving a profound transformation of the future energy mix and widely considered an ideal choice for achieving sustainable energy development.

[0003] Among current hydrogen production technologies, water electrolysis technology, with its unique advantages in process cleanliness, demonstrates enormous potential for application. This technology can be efficiently integrated with renewable energy generation devices such as wind and photovoltaic power generation, enabling flexible energy conversion and storage, effectively addressing the intermittent and volatile nature of renewable energy. This technology aligns with the global trend of green energy transformation, garnering significant attention in the energy sector and boasting broad development prospects. Among these, alkaline water electrolysis technology, due to its mature process, stable operation, low equipment costs, and significant scalability potential, has become a mainstream path for green hydrogen production, occupying a key position in the hydrogen production industry.

[0004] As a core component of the alkaline water electrolysis system, the diaphragm must possess both gas barrier properties and ion conductivity, playing a crucial role in the hydrogen production process. On the one hand, the diaphragm must effectively block cross-permeation between the anode and cathode gases, preventing the explosive mixing of hydrogen and oxygen to ensure the safe and stable operation of the hydrogen production system. On the other hand, the diaphragm must also maintain good electrolyte ion conductivity to ensure the smooth electrolysis reaction and reduce electrolysis energy consumption. Therefore, the performance of the diaphragm is directly related to the efficiency of hydrogen production and the safety of the system operation.

[0005] Currently, the main types of diaphragms used in alkaline water electrolysis technology include asbestos, PPS, and composite diaphragms. Asbestos diaphragms were initially widely used in alkaline water electrolysis for hydrogen production. However, their inherent high electrical resistance increases the energy consumption of the electrolysis process. Furthermore, their poor chemical stability makes them susceptible to chemical changes over long-term use, affecting diaphragm performance. More seriously, asbestos fibers are carcinogenic, posing a health risk to operators. Due to these and other issues, asbestos diaphragms have been gradually phased out of the market. While the recently proposed composite diaphragm combines the toughness and film-forming properties of organic materials with the rigidity and hydrophilicity of inorganic materials, it is expensive and suffers from insufficient interfacial bonding strength. Therefore, it remains in the research stage and has not yet been commercialized. PPS diaphragms, due to their excellent chemical stability (strong alkali and high temperature resistance) and mechanical strength, have become the mainstream industrial diaphragm material. However, PPS diaphragms still suffer from disadvantages such as poor hydrophilicity and low ionic conductivity, which limit their widespread application in high-performance alkaline water electrolysis hydrogen production systems.

[0006] In recent years, a large number of researchers have conducted relevant research on the problems existing in the application of PPS membranes. Their modification strategies mainly focus on surface hydrophilic treatment and structural functional design. Some researchers have proposed that the introduction of sulfonic acid groups through plasma treatment or chemical grafting can improve the hydrophilicity of PPS membranes (the contact angle is reduced from 120° to 30°) and enhance the ion exchange capacity, but the coating is easy to fall off and the long-term operation stability is insufficient. In addition, some researchers have proposed doping TiO2 or ZrO2 nanoparticles to construct porous channels, and their OH⁻ conductivity is increased to 0.15 S / cm, but the problem of nanoparticle agglomeration leads to a decrease in membrane uniformity. Summary of the Invention

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is: A method for modifying and preparing a PPS diaphragm for producing hydrogen by alkaline water electrolysis is provided, comprising the following steps: (1) Using a PPS membrane as a substrate, immerse it in a nitric acid solution, heat and stir it for pickling pretreatment, and then take it out for cleaning and drying; (2) adding dopamine to a 10-50 mM tris(hydroxymethyl)aminomethane hydrochloride solution and stirring to dissolve the solution to prepare a dopamine hydrochloride solution, wherein the concentration of dopamine in the dopamine hydrochloride solution is 0.5-10 g / L; immersing the pretreated substrate in the dopamine hydrochloride solution to perform a dopamine hydrophilization treatment, and reacting for 1-15 hours to form a uniform polydopamine nanoparticle layer on the surface of the PPS diaphragm; (3) After the reaction is completed, the PPS membrane is removed and rinsed with deionized water to fully clean the loosely bound nanoparticles, and then dried to obtain the modified PPS membrane.

[0008] In a preferred embodiment of the present invention, the thickness of the PPS diaphragm is 500-1000 μm.

[0009] In a preferred embodiment of the present invention, in step (1), the concentration of the nitric acid solution is 1-5M.

[0010] In a preferred embodiment of the present invention, in step (1), the heating temperature is 30-100°C, the stirring rate is 200-1500 rpm, and the stirring time is 1-20 h.

[0011] In a preferred embodiment of the present invention, in step (1), after the pickling is completed, the PPS diaphragm is taken out and fully rinsed with deionized water.

[0012] The beneficial effects of the present invention are: effectively improving the hydrophilicity of the PPS membrane, optimizing the pore size distribution of the membrane, and more efficiently exerting the gas barrier and ion conduction functions. In addition, the method has a simple operation process and low cost, which is conducive to promoting the widespread application of PPS membranes in high-performance alkaline water electrolysis hydrogen production systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which: Figure 1 Graph showing contact angles of the PPS membranes prepared in Examples 1-4 of the present invention; Figure 2 This is a test chart of the stability (hydrophilicity maintenance time) of the PPS diaphragms prepared in Examples 1-4 of the present invention; Figure 3 This is a performance diagram of the PPS diaphragm prepared in Example 3 used in an electrolytic cell; Figure 4 Schematic diagram of the appearance of the PPS membrane prepared in Examples 1-4 of the present invention; Figure 5 Schematic diagram of the microstructure of the PPS membrane prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0014] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0015] See also Figure 1-5 , embodiments of the present invention include: A method for preparing a modified PPS diaphragm for producing hydrogen by alkaline water electrolysis, comprising the following steps: (1) Using PPS diaphragm as the substrate, it was pre-treated by pickling, and then cleaned and dried.

[0016] More preferably, the thickness of the PPS separator is 500-1000 μm.

[0017] More preferably, the pickling step comprises: immersing the PPS membrane in a nitric acid solution having a concentration of 1 to 5 M, followed by heating and stirring, wherein the heating temperature is 30 to 100° C., the stirring rate is 200 to 1500 rpm, and the stirring time is 1 to 20 hours.

[0018] More preferably, after the pickling is completed, the PPS diaphragm is taken out and thoroughly rinsed with deionized water.

[0019] (2) Dopamine is added to a 10-50 mM tris(hydroxymethyl)aminomethane hydrochloride solution to prepare a dopamine hydrochloride solution, and the dopamine concentration is adjusted to 0.5-10 g / L; the pretreated substrate is immersed in the dopamine hydrochloride solution to perform dopamine hydrophilization treatment, and the reaction is carried out for 1-15 hours.

[0020] (3) After the reaction is completed, the PPS membrane is removed and rinsed with deionized water to fully clean the loosely bound nanoparticles, and then dried to obtain a modified PPS membrane.

[0021] Dopamine undergoes a self-assembly polymerization reaction to form a highly uniform layer of polydopamine nanoparticles on the surface of the PPS separator. This modified layer stabilizes the polydopamine nanoparticles and the base separator through forces such as hydrogen bonds and π-π covalent bonds. Because the polydopamine nanoparticles in the modified layer contain hydrophilic functional groups such as hydroxyl and amino groups, the hydrophilicity of the separator is significantly enhanced. Furthermore, this modified layer optimizes the pore size distribution of the separator, facilitating more efficient gas barrier and ion conduction.

[0022] The method for modifying the PPS diaphragm of the present invention has a simple operation process, is easy to scale up in industrial applications, and has low cost, which is conducive to further promoting the widespread application of PPS diaphragms in high-performance alkaline water electrolysis hydrogen production systems. Example

[0023] A 500μm thick PPS membrane was immersed in a 1M nitric acid solution and heated and stirred for 8 hours. The temperature was 40°C, the stirring rate was 500 rpm, and the stirring reaction time was 8 hours. After the acid wash, the PPS membrane was removed, rinsed thoroughly with deionized water, and dried in an oven. Dopamine was added to a 10mM tris(hydroxymethyl)aminomethane hydrochloride solution and stirred to dissolve to prepare a dopamine hydrochloride solution. The dopamine concentration was 0.5g / L. The pretreated PPS membrane was quickly immersed in the dopamine hydrochloride solution and reacted in air for 4 hours. After the reaction, the membrane was rinsed with deionized water to thoroughly clean the loosely bound nanoparticles and dried to obtain the modified PPS membrane.

[0024] The contact angle of the PPS membrane prepared in Example 1 is as follows: Figure 1 As shown in Figure 1, its contact angle is 75.2°, which is lower than that of the unmodified PPS membrane and improves its hydrophilicity. The surface resistance, airtightness, tensile strength, and breaking strength of the PPS membrane are shown in Table 1. The surface resistance, airtightness, tensile strength, and breaking strength of the modified PPS membrane are all better than those of the unmodified PPS membrane. This is mainly attributed to the effective improvement of the interaction between the fabric interface by acid washing and dopamine modification.

[0025] In addition, the stability of the PPS membrane was tested by immersing the membrane in a 30% KOH solution at 90°C for 30 days. After the test, the membrane was taken out and the time required for the liquid drop to completely soak into the membrane was tested. Figure 2 The infiltration time of the PPS membrane prepared in Example 1 is 0.88 s, which is better than that of the unmodified membrane. The modified membrane can still maintain stable hydrophilicity when exposed to high-temperature and high-concentration alkali solution for a long time. Example

[0026] A 600μm-thick PPS membrane was immersed in a 1.5M nitric acid solution and heated with stirring for 6 hours at a heating temperature of 50°C and a stirring rate of 800 rpm. After acid washing, the membrane was removed, rinsed thoroughly with deionized water, and dried in an oven. Dopamine was added to a 20mM tris(hydroxymethyl)aminomethane hydrochloride solution and dissolved with stirring to prepare a dopamine hydrochloride solution with a dopamine concentration of 1g / L. The pretreated PPS membrane was quickly immersed in the dopamine hydrochloride solution and reacted in air for 3 hours. After the reaction, the membrane was rinsed with deionized water to thoroughly remove loosely bound nanoparticles and dried to obtain the modified PPS membrane.

[0027] The contact angle of the PPS membrane prepared in Example 2 is as follows: Figure 1As shown in Table 1, the contact angle is 68.5°, and the hydrophilicity is improved. The surface resistance, air tightness, tensile strength and breaking strength of the PPS membrane are shown in Table 1. The surface resistance, air tightness, tensile strength and breaking strength of the modified PPS membrane are better than those of the unmodified PPS membrane. In addition, Figure 2 The wetting time of the PPS membrane prepared in Example 2 is 0.76 s, which is better than that of the unmodified membrane. Example

[0028] An 800μm-thick PPS membrane was immersed in a 2M nitric acid solution and heated and stirred for 4 hours at a temperature of 70°C and a stirring rate of 1000 rpm. After acid washing, the membrane was removed, rinsed thoroughly with deionized water, and dried in an oven. Dopamine was added to a 30mM tris(hydroxymethyl)aminomethane hydrochloride solution and stirred to dissolve to prepare a dopamine hydrochloride solution with a dopamine concentration of 2g / L. The pretreated PPS membrane was quickly immersed in the dopamine hydrochloride solution and reacted in air for 2 hours. After the reaction, the membrane was rinsed with deionized water to thoroughly clean loosely bound nanoparticles and then dried to obtain the modified PPS membrane.

[0029] The contact angle of the PPS membrane prepared in Example 3 is as follows: Figure 1 As shown in the figure, the contact angle is 55.6°, and the hydrophilicity is significantly improved. The surface resistance, air tightness, tensile strength and breaking strength of the modified PPS membrane are better than those of the unmodified PPS membrane. Figure 2 As shown, the wetting time of the PPS membrane prepared in Example 3 is 0.58 s, which is better than that of the unmodified membrane.

[0030] The modified PPS diaphragm prepared in Example 3 and the unmodified PPS diaphragm were used to assemble electrolytic cells for testing. The cathode and anode were made of the same electrode material. The test results are shown in FIG. Figure 3 As shown in the figure, the cell voltage using the modified PPS diaphragm shows better performance under different electrical density conditions. Example

[0031] A 1000μm thick PPS membrane was immersed in a 3M nitric acid solution and heated with stirring for 2 hours at 90°C and a stirring rate of 1200 rpm. After acid washing, the membrane was removed, rinsed thoroughly with deionized water, and dried in an oven. Dopamine was added to a 40mM tris(hydroxymethyl)aminomethane hydrochloride solution and dissolved with stirring to prepare a dopamine hydrochloride solution with a dopamine concentration of 3g / L. The pretreated PPS membrane was quickly immersed in the dopamine hydrochloride solution and reacted in air for 1 hour. After the reaction, the membrane was rinsed with deionized water to thoroughly clean loosely bound nanoparticles and then dried to obtain the modified PPS membrane.

[0032] The contact angle of the PPS membrane prepared in Example 4 is as follows: Figure 1 As shown in the figure, its contact angle is 62.1°, and its hydrophilicity is still better than that of the unmodified PPS membrane. The surface resistance, air tightness, tensile strength and breaking strength of the modified PPS membrane are all better than those of the unmodified PPS membrane. Figure 2 The wetting time of the PPS membrane prepared in Example 2 is 0.67 s, which is better than that of the unmodified membrane.

[0033] Table 1 Surface resistance, air tightness, tensile strength and breaking strength of the prepared PPS separator

[0034] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a modified PPS diaphragm for producing hydrogen by alkaline water electrolysis, characterized in that the steps include: (1) Using a PPS membrane as a substrate, immerse it in a nitric acid solution, heat and stir it for pickling pretreatment, and then take it out for cleaning and drying; (2) adding dopamine to a 10-50 mM tris(hydroxymethyl)aminomethane hydrochloride solution and stirring to dissolve the solution to prepare a dopamine hydrochloride solution, wherein the concentration of dopamine in the dopamine hydrochloride solution is 0.5-10 g / L; immersing the pretreated substrate in the dopamine hydrochloride solution to perform a dopamine hydrophilization treatment, and reacting for 1-15 hours to form a uniform polydopamine nanoparticle layer on the surface of the PPS diaphragm; (3) After the reaction is completed, the PPS membrane is removed and rinsed with deionized water to fully clean the loosely bound nanoparticles, and then dried to obtain the modified PPS membrane.

2. A method for preparing a modified PPS diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, characterized in that: The thickness of the PPS diaphragm is 500-1000 μm.

3. A method for preparing a modified PPS diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, characterized in that: In step (1), the concentration of the nitric acid solution is 1-5M.

4. A method for preparing a modified PPS diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, characterized in that: In step (1), the heating temperature is 30-100°C, the stirring rate is 200-1500 rpm, and the stirring time is 1-20 h.

5. The method for preparing a modified PPS diaphragm for producing hydrogen by alkaline water electrolysis according to claim 1, wherein: In step (1), after the pickling is completed, the PPS diaphragm is taken out and rinsed thoroughly with deionized water.

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