Multistage ionic membrane coupling system and method for producing hydrogen through water electrolysis

Abstract

The invention belongs to the technical field of water electrolysis hydrogen production, and relates to a multistage ionic membrane coupling system and method for water electrolysis hydrogen production. Comprising a raw material water treatment unit, a multi-stage ionic membrane electrolytic cell, a hydrogen side separator and a gradient water replenishing tank, the raw material water treatment unit comprises a reverse osmosis device and an electrodialysis device which are sequentially connected; the electrodialysis device is connected with a first water inlet of the multi-stage ionic membrane electrolytic cell; an anode layer, a composite ion exchange membrane and a cathode layer are sequentially arranged in the multi-stage ion membrane electrolytic bath from bottom to top; a hydrogen outlet is formed in a cathode layer of the multi-stage ionic membrane electrolytic bath; an oxygen outlet is formed in an anode layer of the multi-stage ionic membrane electrolytic bath; the hydrogen outlet is connected with a gas-liquid mixing inlet of the hydrogen side separator; a liquid outlet of the hydrogen side separator is connected with a second water inlet of the multi-stage ionic membrane electrolytic cell; and the gradient water replenishing tank is connected with a liquid inlet of the hydrogen side separator. The effects of reducing the energy consumption, improving the hydrogen purity and enhancing the operation stability are achieved.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis hydrogen production technology, and relates to a multi-stage ion membrane coupling system and method for water electrolysis hydrogen production. Background Technology

[0002] Hydrogen production via water electrolysis is a crucial method for obtaining high-purity hydrogen in modern chemical industry, widely applied in ammonia synthesis, fine chemicals, and clean energy. Traditional alkaline water electrolysis systems typically use asbestos membranes or polymer ion-exchange membranes as electrolyte carriers, decomposing water into hydrogen and oxygen under direct current. A typical system includes an electrolyzer, a gas separation unit, a circulating water circuit, and an external water replenishment module. The electrolyte is usually a KOH or NaOH solution, with a circulating pump maintaining fluid dynamic stability. In recent years, with the development of proton exchange membrane (PEM) technology, membrane electrode assemblies based on perfluorosulfonic acid resin have gradually become the core unit for efficient hydrogen production, possessing advantages such as high current density, high gas purity, and fast response speed.

[0003] However, existing systems have significant drawbacks during long-term operation: metal ions (such as Fe) in the circulating water... 2+ Mg 2+ The continuous accumulation of hydrogen ions (such as oxygen, hydrogen, and nitrogen) leads to increased conductivity, resulting in increased parasitic currents, higher energy consumption, and potential cross-contamination between hydrogen and oxygen. Simultaneously, traditional ion exchange membranes are prone to swelling, affecting mechanical stability and gas barrier performance. The large quantities of precious metal catalysts required result in high costs. Furthermore, reliance on external pumps for liquid circulation and water replenishment further increases system energy consumption and complexity. These problems severely restrict the improvement of energy efficiency and large-scale application of water electrolysis hydrogen production systems. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a multi-stage ion membrane coupling system and method for hydrogen production by water electrolysis, achieving the technical effects of dynamic conductivity control, reduced energy consumption, improved hydrogen purity, and enhanced operational stability.

[0005] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a multi-stage ion membrane coupling system for hydrogen production by water electrolysis, comprising a raw water treatment unit, a multi-stage ion membrane electrolyzer, a hydrogen-side separator, and a gradient water replenishment tank; The raw water treatment unit includes a reverse osmosis unit and an electrodialysis unit connected in sequence; the electrodialysis unit is connected to the first water inlet of the multi-stage ion membrane electrolyzer; the multi-stage ion membrane electrolyzer has an anode layer, a composite ion exchange membrane, and a cathode layer arranged sequentially from bottom to top; a hydrogen outlet is provided on the cathode layer of the multi-stage ion membrane electrolyzer; an oxygen outlet is provided on the anode layer of the multi-stage ion membrane electrolyzer; the hydrogen outlet is connected to the gas-liquid mixing inlet of the hydrogen-side separator; the liquid outlet of the hydrogen-side separator is connected to the second water inlet of the multi-stage ion membrane electrolyzer; and the gradient makeup water tank is connected to the liquid inlet of the hydrogen-side separator.

[0006] Preferably, the method for preparing the composite ion exchange membrane is as follows: A blended base film was obtained by extruding a mixture of perfluorosulfonic acid resin and zirconium oxychloride. The blended base membrane is immersed in a sulfonation solution for surface treatment, and then dried to obtain the composite ion exchange membrane.

[0007] Preferably, the mass ratio of the perfluorosulfonic acid resin to zirconium oxychloride is 4:1.

[0008] Preferably, the sulfonated liquid is prepared by mixing concentrated sulfuric acid with hydrogen peroxide and stirring to obtain the sulfonated liquid.

[0009] Preferably, the anode layer is prepared by: A perfluorosulfonic acid solution was added to an isopropanol solution, followed by the addition of nickel-iron layered double hydroxide and iridium dioxide powder. After dispersion and mixing, an electrode core-shell catalyst was obtained. The electrode core-shell catalyst was loaded onto the surface of a titanium mesh and dried to obtain the anode layer.

[0010] Preferably, the ratio of the nickel-iron layered double hydroxide, iridium dioxide powder, perfluorosulfonic acid solution and isopropanol solution is 5g:5g:1mL:20mL.

[0011] Preferably, the cathode layer is made of a platinum catalyst and a carbon catalyst.

[0012] Preferably, the inner wall of the hydrogen-side separator is coated with a conductivity modifier layer.

[0013] Preferably, the method for preparing the conductivity modifier layer is as follows: Sulfonated polyether ether ketone and sulfonated zirconium oxide are mixed to obtain a slurry; the slurry is coated on the inner wall of the hydrogen-side separator 3, and after curing, it forms the conductivity modifier layer.

[0014] Secondly, the present invention provides a multi-stage ion membrane coupling method for hydrogen production by water electrolysis, comprising the following steps: Raw water is introduced into the raw water treatment unit and treated by reverse osmosis and electrodialysis to obtain ultrapure water; The ultrapure water is introduced into the first water inlet of a multi-stage ion membrane electrolyzer; in the multi-stage ion membrane electrolyzer, the water undergoes an electrochemical reaction between the anode layer and the cathode layer to generate hydrogen and oxygen. The hydrogen gas is discharged from the hydrogen outlet of the cathode layer along with the liquid phase and enters the hydrogen-side separator; gaseous hydrogen gas and electrolyte-containing circulating liquid are separated in the hydrogen-side separator; the circulating liquid is returned to the second water inlet of the multi-stage ion membrane electrolyzer through the liquid outlet of the hydrogen-side separator. When the liquid level in the hydrogen-side separator is lower than the set threshold, the gradient water replenishment tank is activated to replenish ultrapure water into the hydrogen-side separator.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention effectively removes metal ions from the feed water, reduces initial conductivity, and minimizes parasitic current loss by incorporating a feed water treatment unit that includes reverse osmosis and electrodialysis. It employs a composite ion exchange membrane to enhance proton conduction efficiency, suppress swelling, and improve gas barrier properties. Combined with a conductivity modifier layer coated on the inner wall of the hydrogen-side separator, it adsorbs metal ions in the circulating liquid in real time, preventing their accumulation that could lead to increased conductivity and catalyst poisoning. Furthermore, a gradient water replenishment tank enables pump-free gravity water replenishment, reducing system energy consumption. This invention achieves the technical benefits of reduced energy consumption, increased hydrogen purity, and enhanced operational stability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to the present invention; Figure 2 This is a cross-sectional schematic diagram of the multi-stage ion membrane electrolyzer of the present invention.

[0018] The components include: 1. Raw water treatment unit; 2. Multi-stage ion membrane electrolyzer; 21. Anode layer; 22. Composite ion exchange membrane; 23. Cathode layer; 3. Hydrogen-side separator; 4. Gradient water replenishment tank. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings: The first objective of this invention is to provide a multi-stage ion membrane coupling system for hydrogen production via water electrolysis, such as... Figures 1-2 As shown, it includes a raw water treatment unit 1, a multi-stage ion membrane electrolyzer 2, a hydrogen-side separator 3, and a gradient water replenishment tank 4; The raw water treatment unit 1 includes a reverse osmosis unit and an electrodialysis unit connected in sequence; the electrodialysis unit is connected to the first water inlet of the multi-stage ion membrane electrolyzer 2; the multi-stage ion membrane electrolyzer 2 is provided with an anode layer 21, a composite ion exchange membrane 22 and a cathode layer 23 arranged in sequence from bottom to top; a hydrogen outlet is provided on the cathode layer 23 of the multi-stage ion membrane electrolyzer 2; an oxygen outlet is provided on the anode layer 21 of the multi-stage ion membrane electrolyzer 2; the hydrogen outlet is connected to the gas-liquid mixing inlet of the hydrogen-side separator 3; the liquid outlet of the hydrogen-side separator 3 is connected to the second water inlet of the multi-stage ion membrane electrolyzer 2; and the gradient makeup water tank 4 is connected to the liquid inlet of the hydrogen-side separator 3.

[0026] The raw water treatment unit 1 is used to pretreat the raw water source. First, a reverse osmosis device removes most dissolved solids, organic matter, and microorganisms. Then, an electrodialysis device further removes residual ions, especially monovalent and divalent metal cations, to obtain ultrapure water with a conductivity of less than 1 μS / cm. This ultrapure water is piped to the first water inlet of the multi-stage ion-exchange membrane electrolyzer 2 as the initial feed water for the electrolysis reaction. The multi-stage ion-exchange membrane electrolyzer 2 has a vertically arranged layered structure, with an anode layer 21, a composite ion-exchange membrane 22, and a cathode layer 23 arranged sequentially from bottom to top, forming a complete electrolysis cell unit. Under energized conditions, the anode layer 21 catalyzes the oxidation of water molecules to generate oxygen, which is discharged through a dedicated channel from the oxygen outlet on the anode layer 21. The cathode layer 23 catalyzes a reduction reaction to generate hydrogen, which, in the form of bubbles, carries some unreacted water out from the hydrogen outlet of the cathode layer 23 and enters the downstream hydrogen-side separator 3. The hydrogen outlet is directly connected to the gas-liquid mixing inlet of the hydrogen-side separator 3, allowing moist hydrogen to be smoothly introduced into the separator's inner cavity. Under gravity or inertia, gas-liquid two-phase separation is achieved: the gaseous hydrogen is discharged from the top for subsequent collection or utilization, while the liquid phase accumulates at the bottom and returns to the second water inlet of the multi-stage ion membrane electrolyzer 2 through the liquid outlet, forming a closed-loop circulation path, reducing water waste and maintaining electrolyte stability. The gradient water replenishment tank 4 is located above the hydrogen-side separator 3, and its outlet is connected to the liquid inlet of the hydrogen-side separator 3. When the liquid level in the hydrogen-side separator 3 drops below a set threshold due to evaporation or drainage during system operation, automatic replenishment is initiated based on the static pressure difference. This allows for water replenishment without additional power equipment, achieving pump-free operation.

[0027] For example, the preparation method of the composite ion exchange membrane 22 is as follows: Perfluorosulfonic acid resin and zirconium oxychloride were blended at a mass ratio of 4:1 and then extruded to obtain a blended base film. The blended base membrane was immersed in a sulfonation solution for surface treatment and dried to obtain the composite ion exchange membrane 22.

[0028] In this process, perfluorosulfonic acid resin serves as the proton-conducting matrix material, providing continuous hydrophilic channels to support efficient proton transport. Zirconium oxychloride, as an inorganic filler, is introduced into the polymer matrix to form a uniformly dispersed nanoscale rigid network structure during film formation, effectively suppressing excessive movement of polymer chain segments in the hydrated state, thereby reducing the swelling tendency of the membrane material under electrolysis conditions. Subsequently, the blended membrane is surface-treated with sulfonation solution to construct a high-density sulfonate group region on the membrane surface, enhancing the proton jumping conduction ability at the interface, improving the contact matching between the membrane and the electrode, and reducing the interfacial resistance.

[0029] In practical applications, blending can be performed using a twin-screw extruder under controlled temperature conditions for melt mixing, or by ultrasonic-assisted dispersion in a polar solvent followed by casting. The particle size of zirconium oxychloride is controlled within the range of 50 nm to 500 nm to ensure good dispersion in the matrix and to leverage its size effect. The extrusion molding temperature is set between 70°C and 100°C to suit the processing characteristics of perfluorosulfonic acid resins and prevent thermal degradation. The thickness of the resulting blended base film can be adjusted according to actual application requirements, typically ranging from 50 μm to 200 μm, balancing mechanical strength and mass transfer efficiency. During surface treatment, the temperature is controlled between 40°C and 60°C, and the time is maintained between 1 h and 3 h. Oscillation at a frequency of approximately 10 Hz helps ensure reaction uniformity. The drying process is carried out at 40°C to 80°C using vacuum drying to avoid residual moisture causing bubbles or delamination during subsequent hot pressing. The drying time is adjusted according to the film thickness, generally ranging from 15 min to 60 min.

[0030] The sulfonation solution is prepared by mixing concentrated sulfuric acid (95%–98% by mass) and hydrogen peroxide (30%–35% by mass) at a volume ratio of 4:1 and stirring to obtain the sulfonation solution. Concentrated sulfuric acid, as a strong protic acid, provides effective sulfonation capability, causing electrophilic substitution reactions of carbon atoms in the polymer chain to form –SO3H groups. Hydrogen peroxide, as a mild oxidant, not only participates in the free radical initiation reaction, promoting the grafting efficiency of sulfonic acid groups on the polymer surface, but also regulates the redox balance in the reaction environment, preventing the main chain structure from breaking or cross-linking due to excessive oxidation.

[0031] For example, the anode layer 21 is prepared by: Perfluorosulfonic acid solution was added to isopropanol solution, and then nickel-iron layered double hydroxide and iridium dioxide powder were added. After dispersion and mixing, the electrode core-shell catalyst was obtained. The electrode core-shell catalyst was loaded onto the surface of titanium mesh and dried to obtain anode layer 21.

[0032] Among them, nickel-iron layered double hydroxides serve as the catalyst core, providing a high specific surface area and abundant active sites for oxygen evolution reaction. Iridium dioxide powder forms an ultra-thin catalytic shell on the periphery, significantly improving oxygen evolution kinetics and reducing the amount of precious metals used. Perfluorosulfonic acid solution acts as a binder in the system and also constructs a proton conduction network, enhancing the proton transport capacity of the electrode interface. Isopropanol solution serves as a dispersion medium to adjust the viscosity of the slurry, ensuring good flowability and atomization characteristics during spraying and avoiding gun clogging or uneven coating.

[0033] Furthermore, the ratio of nickel-iron layered double hydroxide, iridium dioxide powder, perfluorosulfonic acid solution, and isopropanol solution is 5g:5g:1mL:20mL. This ratio range has a moderate solid content, good stability of the slurry system, and can maintain a uniform suspension state for a long time after ultrasonic dispersion, making it suitable for automated spraying processes.

[0034] The cathode layer 23 is made of platinum and carbon catalysts. The platinum catalyst refers to a catalytic material with platinum as the main active component, which can exist in the form of being supported on a conductive carrier. Typically, it consists of nanoscale platinum particles uniformly distributed on a carbon matrix with a high specific surface area. Due to its d-orbital electronic structure, platinum has a moderate adsorption energy for hydrogen atoms, exhibiting extremely high intrinsic activity for the hydrogen evolution reaction, and can drive efficient hydrogen production at relatively low overpotentials. The carbon catalyst here does not refer to a non-noble metal carbon material (such as nitrogen-doped carbon) that plays a dominant catalytic role, but rather functions as a support for the platinum catalyst; that is, a platinum-carbon composite catalytic system is actually used.

[0035] The inner wall of the hydrogen-side separator 3 is coated with a conductivity modifier layer. The conductivity modifier layer is prepared by mixing sulfonated polyether ether ketone with sulfonated zirconium oxide to obtain a slurry; coating the slurry onto the inner wall of the hydrogen-side separator 3, and curing it to form a conductivity modifier layer.

[0036] The conductivity modifier layer is a functional coating with ion exchange capabilities. Its main function is to capture metal cations, such as Fe, dissolved in the circulating liquid due to electrolysis or material corrosion without altering the original separation process. 2+ Ca 2+ Mg 2+ These ions, if not removed in time, will accumulate in the closed-loop cycle, leading to increased system conductivity and consequently causing problems such as parasitic current, increased energy loss, catalyst poisoning, and membrane material aging. This coating works through a dual mechanism of physical retention and chemical adsorption: on the one hand, its microporous structure can retain some particulate impurities; on the other hand, the sulfonic acid groups abundant in the coating can selectively bind divalent and higher-valent metal cations through electrostatic attraction and ion exchange, significantly reducing the ion concentration in the circulating liquid.

[0037] A second objective of this invention is to provide a multi-stage ion membrane coupling method for hydrogen production via water electrolysis, comprising the following steps: Raw water is introduced into raw water treatment unit 1 and then passed through a reverse osmosis device and an electrodialysis device in sequence to effectively remove dissolved solids and metal ions, resulting in ultrapure water with a conductivity of less than 1 μS / cm. Ultrapure water is introduced into the first water inlet of the multi-stage ion-exchange membrane electrolyzer 2. Within the multi-stage ion-exchange membrane electrolyzer 2, water undergoes an electrochemical reaction between the anode layer 21 and the cathode layer 23. The specific electrode reactions are as follows:

[0038] This produces hydrogen and oxygen. Hydrogen generated at the cathode is discharged from the hydrogen outlet of the cathode layer 23 along with the unreacted liquid phase and enters the hydrogen-side separator 3 together. In the hydrogen-side separator 3, centrifugal force is used to achieve efficient separation of gaseous hydrogen and electrolyte-containing circulating liquid. At the same time, the conductivity regulator layer coated on the inner wall of the hydrogen-side separator 3 can actively adsorb metal ions in the circulating liquid, prevent catalyst poisoning, and extend the service life of the system. The separated gaseous hydrogen is discharged from the system as a product; the separated circulating liquid sinks to the bottom of the hydrogen-side separator 3 and returns to the second water inlet of the multi-stage ion membrane electrolyzer 2 through its liquid outlet, realizing the recycling of water and electrolyte. The liquid level in the hydrogen-side separator 3 is monitored in real time by a water level sensor. When the liquid level is lower than the set threshold, the system first opens the valve to balance the internal pressure of the gradient water supply tank 4, and then activates the gravity water supply valve to replenish ultrapure water into the hydrogen-side separator 3; after the liquid level returns to the normal range, all valves are closed, and the system continues the water electrolysis hydrogen production reaction.

[0039] In this invention, the raw water undergoes dual purification via reverse osmosis and electrodialysis to ensure feed water quality. Hydrogen generated by electrolysis carries a small amount of liquid into a hydrogen-side separator for gas-liquid separation. The separated circulating liquid returns to the electrolyzer to continue participating in the reaction, forming a closed-loop system with high resource utilization. When the system liquid level is insufficient, a gradient water replenishment tank automatically replenishes ultrapure water using gravity, eliminating pump energy consumption. This method solves the technical problems of traditional systems, such as reliance on manual water replenishment, difficulty in maintaining water quality, and high energy consumption, significantly improving operational stability and energy utilization efficiency. It is particularly suitable for large-scale green hydrogen production scenarios requiring long-term continuous operation.

[0040] Example 1 This embodiment provides a multi-stage ion membrane coupling system for hydrogen production by water electrolysis, including a raw water treatment unit 1, a multi-stage ion membrane electrolyzer 2, a hydrogen-side separator 3, and a gradient water replenishment tank 4; Raw water treatment unit 1 includes a reverse osmosis unit and an electrodialysis unit connected in sequence; The multi-stage ion membrane electrolyzer 2 is equipped with an anode layer 21, a composite ion exchange membrane 22 and a cathode layer 23. The inner wall of the hydrogen-side separator 3 is coated with a conductivity modifier layer; The gradient water supply tank 4 is positioned above the hydrogen-side separator 3 and connected to its liquid inlet.

[0041] The composite ion exchange membrane 22 is prepared through the following steps: 100g of perfluorosulfonic acid resin and 25g of zirconium oxychloride were blended and extruded to obtain a blended base film. The blended base membrane was immersed in sulfonation solution, and then washed with water and dried to obtain composite ion exchange membrane 22.

[0042] Anode layer 21 is prepared by the following steps: Add 10 mL of perfluorosulfonic acid solution to 200 mL of isopropanol, then add 50 g of nickel-iron layered double hydroxide and 50 g of iridium dioxide powder, disperse and mix well to obtain catalyst slurry; The catalyst slurry was loaded onto the surface of a titanium mesh and dried to obtain the anode layer 21.

[0043] The conductivity modifier layer on the inner wall of the hydrogen-side separator 3 is prepared through the following steps: Sulfonated polyether ether ketone was mixed with sulfonated zirconium oxide to obtain a slurry; The slurry is coated onto the inner wall of the hydrogen-side separator 3 and cured to form a conductivity modifier layer.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that zirconium oxychloride is not used; the perfluorosulfonic acid resin is directly extruded and molded.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that the inner wall of the hydrogen-side separator 3 is not coated with a conductivity modifier layer.

[0046] The multi-stage ion membrane coupling systems prepared in Example 1 and Comparative Examples 1-2 were tested for hydrogen production via water electrolysis. The test results are shown in Table 1. Table 1. Test results of the multi-stage ion membrane coupling systems prepared in Example 1 and Comparative Examples 1-2

[0047] As can be seen from the comparison of test data in Table 1, the multi-stage ion membrane coupling system prepared in Example 1 of this invention is significantly superior to the comparative example in terms of conductivity, energy consumption, and hydrogen purity. Specifically, the system conductivity is stably maintained at a low level of 1.2~1.5 μS / cm, and the energy consumption is only 4.1 kWh / Nm. 3H2, with a hydrogen purity of up to 99.995%. This superior performance is attributed to the synergistic effect of several innovative designs in the system: the conductivity adjustment layer integrated in the hydrogen-side separator can adsorb metal ions in real time, effectively maintaining water quality and extending the system's lifespan; the composite ion exchange membrane effectively improves proton exchange efficiency while suppressing membrane swelling behavior; in addition, the core-shell electrode catalyst used significantly reduces the amount of precious metals used while ensuring catalytic activity, achieving overall cost optimization.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-stage ion-membrane coupling system for hydrogen production by water electrolysis, characterized in that, It includes a raw water treatment unit (1), a multi-stage ion membrane electrolyzer (2), a hydrogen-side separator (3), and a gradient water replenishment tank (4); The raw water treatment unit (1) includes a reverse osmosis device and an electrodialysis device connected in sequence; the electrodialysis device is connected to the first water inlet of the multi-stage ion membrane electrolyzer (2); the multi-stage ion membrane electrolyzer (2) is provided with an anode layer (21), a composite ion exchange membrane (22) and a cathode layer (23) from bottom to top; a hydrogen outlet is provided on the cathode layer (23) of the multi-stage ion membrane electrolyzer (2); an oxygen outlet is provided on the anode layer (21) of the multi-stage ion membrane electrolyzer (2); the hydrogen outlet is connected to the gas-liquid mixing inlet of the hydrogen-side separator (3); the liquid outlet of the hydrogen-side separator (3) is connected to the second water inlet of the multi-stage ion membrane electrolyzer (2); the gradient water replenishment tank (4) is connected to the liquid inlet of the hydrogen-side separator (3).

2. The multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 1, characterized in that, The method for preparing the composite ion exchange membrane (22) is as follows: A blended base film was obtained by extruding a mixture of perfluorosulfonic acid resin and zirconium oxychloride. The blended base membrane is immersed in a sulfonation solution for surface treatment and then dried to obtain the composite ion exchange membrane (22).

3. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 2, characterized in that, The mass ratio of the perfluorosulfonic acid resin to zirconium oxychloride is 4:

1.

4. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 2, characterized in that, The sulfonated solution is prepared by mixing concentrated sulfuric acid with hydrogen peroxide and stirring to obtain the sulfonated solution.

5. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 1, characterized in that, The anode layer (21) is prepared by: Perfluorosulfonic acid solution was added to isopropanol solution, and then nickel-iron layered double hydroxide and iridium dioxide powder were added. After dispersion and mixing, the electrode core-shell catalyst was obtained. The electrode core-shell catalyst was loaded onto the surface of a titanium mesh and dried to obtain the anode layer (21).

6. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 5, characterized in that, The ratio of the nickel-iron layered double hydroxide, iridium dioxide powder, perfluorosulfonic acid solution, and isopropanol solution is 5g:5g:1mL:20mL.

7. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 1, characterized in that, The cathode layer (23) is made of platinum catalyst and carbon catalyst.

8. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 1, characterized in that, The inner wall of the hydrogen-side separator (3) is coated with a conductivity modifier layer.

9. A multi-stage ion membrane coupling system for hydrogen production by water electrolysis according to claim 8, characterized in that, The method for preparing the conductivity modifier layer is as follows: Sulfonated polyether ether ketone and sulfonated zirconium oxide are mixed to obtain a slurry; the slurry is coated on the inner wall of the hydrogen-side separator (3) and cured to form the conductivity modifier layer.

10. A multi-stage ion-membrane coupling method for hydrogen production by water electrolysis, characterized in that, The system based on any one of claims 1 to 9 includes the following steps: Raw water is introduced into the raw water treatment unit (1) and ultrapure water is obtained after reverse osmosis and electrodialysis treatment; The ultrapure water is introduced into the first water inlet of the multi-stage ion membrane electrolyzer (2); in the multi-stage ion membrane electrolyzer (2), the water undergoes an electrochemical reaction between the anode layer (21) and the cathode layer (23) to generate hydrogen and oxygen. The hydrogen gas is discharged from the hydrogen outlet of the cathode layer (23) along with the liquid phase and enters the hydrogen-side separator (3); gaseous hydrogen gas and electrolyte-containing circulating liquid are separated in the hydrogen-side separator (3); the circulating liquid is returned to the second water inlet of the multi-stage ion membrane electrolyzer (2) through the liquid outlet of the hydrogen-side separator (3); When the liquid level in the hydrogen-side separator (3) is lower than the set threshold, the gradient water supply tank (4) is turned on to replenish ultrapure water into the hydrogen-side separator (3).

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