Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 / NF catalysts, their preparation methods and applications

Abstract

This invention discloses Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 This paper discusses / NF catalysts, their preparation methods, and applications, belonging to the field of catalyst synthesis technology. Using large-size nickel foam as a substrate, Ni₂Fe(SO₄) is directly prepared through one-step in-situ microwave-driven growth. 0.5 (OH)6(H2O) 3.85 The nanosheet array eliminates the need for subsequent loading or additional processing, simplifying the process and enhancing the bond between the catalyst and the substrate. This catalyst exhibits excellent performance in hydrogen production via water electrolysis, particularly in seawater electrolysis.

Description

Technical Field

[0001] This invention belongs to the field of catalyst synthesis technology, specifically relating to a Ni2Fe(SO4) catalyst. 0.5 (OH)6(H2O) 3.85 / NF catalysts, their preparation methods, and applications. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Layered double hydroxides (LDHs) are a core research area for non-precious metal oxygen evolution reaction (OER) catalysts due to their advantages such as strong tunability of metal cations, large specific surface area, and low raw material cost. Their "layer-interlayer" structure allows for optimization of catalytic activity by adjusting the metal composition, and the abundant reserves of constituent elements such as Ni and Fe naturally meet the cost requirements of industrial mass production, demonstrating significant application potential in alkaline water electrolysis for hydrogen production.

[0004] Among them, NiFe-based LDHs have become a research focus in this field due to their optimal balance between activity and stability. For example, existing technologies have disclosed the successful preparation of Ni2Fe(SO4) using a seed-assisted heterogeneous nucleation strategy (reaction at 25°C for 24 hours). 0.5 (OH)6(H2O) 3.85 The / NF catalyst (CAPist-L1) provides a key reference for the design of industrial-grade water electrolysis catalysts, and also enables the development of Ni2Fe(SO4). 0.5 (OH)6(H2O) 3.85 This specific phase has become a candidate for industrial catalysts.

[0005] However, existing technologies still face multiple bottlenecks in the development of catalysts with this high-performance phase, making it difficult to transform laboratory results into practical industrial solutions: (1) The contradiction between synthesis efficiency and phase accuracy: The mainstream methods for preparing this catalyst (such as the room temperature impregnation method disclosed in the existing technology) require a lengthy reaction of 24 hours, which is difficult to meet the time requirements for industrial mass production; other common methods for LDH (hydrothermal method, co-precipitation method, etc.) also have problems such as high energy consumption, complex processes, impure phases, and inability to accurately control morphology, which directly affect the stability of catalytic performance. (2) The gap in the expansion of scenario stability: The stability of this material has only been verified in alkaline freshwater systems, while its corrosion resistance and anti-scaling performance in seawater have not been effectively verified; at the same time, the material prepared by the existing process has a long-term high current density (≥1000 mA cm⁻¹) -2Even with these limitations, performance degradation due to mass transfer constraints and structural collapse remains a concern, making it difficult to meet the dual requirements of industrial hydrogen production for both capacity and stability.

[0006] In summary, regarding Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 The synthesis of / NF catalysts, a specific phase, still faces challenges due to current technologies that cannot simultaneously address the core pain points of low synthesis efficiency, difficulty in composition control, poor compatibility with large-size substrates, and insufficient stability in seawater environments. This hinders their practical application in industrial-scale water electrolysis for hydrogen production. Therefore, developing a preparation method for this phase catalyst that is "rapidly synthesized, has controllable composition, is adaptable to large-size substrates, and is compatible with seawater systems" is crucial for its transformation from laboratory testing to industrial application. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a Ni2Fe(SO4) solution. 0.5 (OH)6(H2O) 3.85 / NF catalysts, their preparation methods, and applications.

[0008] This invention enables the one-step in-situ synthesis of Ni2Fe(SO4). 0.5 (OH)6(H2O) 3.85 / NF catalyst, using large-size nickel foam as a substrate, directly prepares Ni2Fe(SO4) through microwave-driven one-step in-situ growth. 0.5 (OH)6(H2O) 3.85 Nanosheet arrays, requiring no subsequent loading or additional processing, simplify the process and enhance the adhesion between the catalyst and the substrate. This represents a groundbreaking, rapid synthesis, and the invention is the first to propose this specific composition (Ni2Fe(SO4)). 0.5 (OH)6(H2O) 3.85 This invention presents a rapid microwave synthesis method for catalysts, filling a gap in existing technologies. It also achieves a breakthrough in efficiency; compared to the lengthy 24-hour process of the traditional impregnation method, this method (including pretreatment) significantly reduces the total time, with the core synthesis requiring only 30 minutes, resulting in an experimental efficiency increase of nearly 50 times. Furthermore, this invention employs a dual-solvent-process adaptation design, using an isopropanol + deionized water dual-solvent system to dissolve the precursor, coupled with microwave parameters of 2000W power and 60℃, precisely adapting to the nucleation and growth of the target catalyst and avoiding Fe... 2+ The oxidation process and precursor dispersion are uneven. Furthermore, this invention achieves precise control of sulfate doping via Fe(SO4)2. Using 9H2O as both an iron source and a sulfate donor, the precise synthesis of sulfate-doped LDH derivatives can be achieved in one step without the need for additional doping steps.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] In a first aspect, the present invention provides a Ni2Fe(SO4) solution. 0.5 (OH)6(H2O) 3.85 The preparation method of / NF catalyst, using microwave synthesis, specifically includes the following steps: Nickel salt and iron salt are dissolved separately in a solvent, mixed together, and then a cationic surfactant is added to obtain a precursor solution. The pretreated nickel foam was immersed in the precursor solution and then placed in a microwave reaction vessel for microwave reaction. The microwave reaction temperature is 40~100℃, and the reaction time is 10~60 minutes.

[0011] In one or more embodiments, the pretreatment process for nickel foam includes: substrate cutting and trimming, multi-step ultrasonic cleaning and activation, and vacuum drying. The multi-step ultrasonic cleaning and activation includes sequential acid pickling with ultrasound, alcohol washing, and water washing. The specific process is conventional in the art and is not specifically limited herein.

[0012] In one or more embodiments, the iron salt is a sulfate and the nickel salt is a nitrate.

[0013] In one or more embodiments, the nickel salt is dissolved in a first solvent, which includes isopropanol. The ratio of nickel salt to the first solvent is (30-50 mmol):(150-250 mL), preferably (35-45 mmol):(180-220 mL).

[0014] In one or more embodiments, the iron salt is dissolved in a second solvent, the second solvent comprising water. The ratio of the iron salt to the second solvent is (10-30 mmol):(50-150 mL), preferably (15-25 mmol):(80-120 mL).

[0015] In one or more embodiments, the molar ratio of nickel salt, iron salt and cationic surfactant is (30~50):(10~30):(5~15), preferably (35~45):(15~25):(8~12).

[0016] In one or more embodiments, the cationic surfactant includes CTAB (hexadecyltrimethylammonium bromide).

[0017] In one or more embodiments, the preparation of the precursor solution specifically includes: dissolving a Ni salt in a first solvent, dissolving an Fe salt in a second solvent, rapidly mixing the two solutions, adding a cationic surfactant, and then subjecting the mixture to ultrasonic treatment for 0.5 to 5 minutes.

[0018] In one or more embodiments, the pretreated nickel foam is completely immersed in the precursor solution for 2 to 10 minutes, preferably 4 to 6 minutes. Sufficient immersion time ensures that the nickel foam is fully wetted by the solution, thereby preventing areas from remaining uncontacted by the reaction solution.

[0019] In one or more embodiments, the microwave reaction vessel is made of high borosilicate material and is an open, sealable container.

[0020] In one or more embodiments, the microwave reaction power is 1000~3000W, specifically 1000W, 1100W, 1200W, 1500W, 1700W, 1800W, 2000W, 2200W, 2500W, etc., preferably 1500~2500W, more preferably 1800~2200W.

[0021] In one or more embodiments, the microwave reaction temperature can specifically be 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., preferably 50~70°C. The reaction time can specifically be 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc., preferably 20~40min.

[0022] In one or more embodiments, the microwave reaction is followed by rinsing and drying.

[0023] The specific rinsing steps are as follows: rinse repeatedly with water and anhydrous ethanol to remove unreacted precursors and byproducts adsorbed on the surface.

[0024] The drying process is vacuum drying, performed at 50~70℃ for 10~15 hours.

[0025] Secondly, the present invention provides a Ni2Fe(SO4) solution. 0.5 (OH)6(H2O) 3.85 The / NF catalyst was prepared by the method described above. NF refers to nickel foam, in which Ni2Fe(SO4) is supported on a nickel foam substrate. 0.5 (OH)6(H2O) 3.85 .

[0026] The catalyst surface exhibits a continuous nanosheet array structure: the sheet thickness is in the nanometer range, and they are interwoven to form a porous three-dimensional network.

[0027] Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85It is evenly covered on the surface of the nickel foam substrate, with a dense and uniform overall morphology, presenting a regular light green color, without local color difference, agglomeration or other unevenness.

[0028] Thirdly, the present invention provides the aforementioned Ni2Fe(SO4). 0.5 (OH)6(H2O) 3.85 The application of / NF catalyst in water electrolysis is preferably in seawater electrolysis. The water is any one of fresh water, seawater, alkaline fresh water, or alkaline seawater.

[0029] Fourthly, the present invention provides a method for producing hydrogen by electrolysis of water, comprising the following steps: using the above-mentioned Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 The / NF catalyst is used as the working electrode for water electrolysis. A three-electrode system can be used, with the Hg / HgO electrode as the reference electrode and the carbon rod as the counter electrode; these electrodes are placed in the electrolyte.

[0030] The electrolyte includes fresh water, seawater, alkaline fresh water, or alkaline seawater.

[0031] Fifthly, the present invention provides an electrolytic cell comprising an anode, a cathode, and an electrolyte, wherein the anode comprises the aforementioned Ni2Fe(SO4). 0.5 (OH)6(H2O) 3.85 / NF catalyst, wherein the electrolyte is any one of fresh water, seawater, alkaline fresh water or alkaline seawater.

[0032] One or more of the above technical solutions have the following advantages or beneficial effects: (1) Breakthrough improvement in synthesis efficiency: The microwave synthesis method provided by this invention has been used to prepare Ni2Fe(SO4). 0.5 (OH)6(H2O) 3.85 / NF catalysts require only 30 minutes for core synthesis, which is more than 98% shorter than the traditional impregnation method which takes 24 hours, and the synthesis efficiency is increased by nearly 50 times. It eliminates the need for multiple post-processing steps such as calcination and etching, simplifies the process, reduces energy consumption by more than 80%, and meets the needs of industrial mass production.

[0033] (2) Significantly optimized synthesis controllability: The "isopropanol + deionized water" dual solvent system was used to rapidly dissolve Ni(NO3)2. 6H2O and Fe(SO4)2 9H2O effectively prevents Fe 2+ Oxidation resulted in uniform dispersion of the precursor; combined with microwave parameters of 2000W power and 60℃, nucleation and crystal growth were precisely driven, successfully preparing Ni2Fe(SO4) with a uniform structure.0.5 (OH)6(H2O) 3.85 Nanosheet arrays enable targeted control of sulfate doping, filling a gap in existing technologies.

[0034] (3) Enhanced substrate compatibility and bonding strength: For large-size nickel foam substrates of 5cm×10cm, the pretreatment process of multi-step ultrasonic cleaning and room temperature vacuum drying ensures the uniformity of substrate activation and avoids secondary oxidation; the catalyst grows in situ on the substrate surface without the need for binder, the interface bonding strength is significantly improved, and there is no shedding under high current density, which is compatible with the size requirements of industrial electrolysis equipment.

[0035] (4) Comprehensive optimization of catalyst performance: 1) Improved active sites and conductivity: The nanosheet array morphology reduces the stacking of layers, and the exposure of active sites is increased by more than 30% compared with traditional LDH; sulfate intercalation optimizes the electronic environment, reduces charge transfer resistance by more than 40%, accelerates OER reaction kinetics, and the Tafel slope can be reduced to 40mV dec -1 The following are examples: 2) Enhanced structural stability: Some crystalline structures possess both activity and stability, avoiding the scarcity of active sites caused by high crystallinity or structural collapse caused by low crystallinity; 3) High current density adaptability meets standards: Meets industrial-grade high current density (≥1000 mA / cm²) requirements. 2 Under these conditions, it can operate stably for over 100 hours with a performance degradation rate of ≤5%, meeting the dual requirements of industrial hydrogen production for both capacity and long-term stability. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 Microwave synthesis of Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 X-ray diffraction (XRD) pattern of the catalyst; Figure 2 Microwave synthesis of Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 Scanning electron microscope (SEM) image of / NF catalyst (magnification × 18.0k); Figure 3 The invention illustrates the microwave synthesis of Ni2Fe(SO4). 0.5 (OH)6(H2O) 3.85 A schematic diagram of the "one-step liquid phase microwave method" process used for / NF catalysts; Figure 4This is the Ni2Fe(SO4) prepared according to the present invention. 0.5 (OH)6(H2O) 3.85 Physical appearance image of the / NF catalyst; Figure 5 This is the Ni2Fe(SO4) prepared according to the present invention. 0.5 (OH)6(H2O) 3.85 Electrochemical performance tests of / NF catalysts for oxygen evolution reaction (OER) and the current density-potential polarization curves obtained in various regions; Figure 6 It is Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 Electrochemical stability test curves of / NF catalysts for oxygen evolution reaction (OER); Figure 7 Linear scanning voltammetric curves comparing the oxygen evolution reaction in seawater of the catalyst prepared by microwave synthesis in Example 1 and the catalyst prepared by long-term room temperature impregnation in Comparative Example 1. Figure 8 This is a comparison of the electrochemical corrosion resistance of the catalyst prepared by microwave synthesis in Example 1 of the present invention and the catalyst prepared by long-term room temperature impregnation in Comparative Example 1. Figure 9 The effect of different reaction times on catalyst performance in microwave synthesis; Figure 10 The effect of different reaction temperatures on catalyst performance in microwave synthesis; Figure 11 The images show a comparison of the morphology of the catalyst with and without the addition of CTAB; where (a) is without CTAB and (b) is with CTAB. Figure 12 Comparison of the effects of CTAB addition on the oxygen evolution reaction of the prepared catalyst; Figure 13 It is Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 Electrochemical stability test curves of / NF catalyst in oxygen evolution reaction (OER) in alkaline seawater. Detailed Implementation

[0038] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0039] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0040] Example 1 1. Activation pretreatment process for nickel foam substrate To achieve in-situ growth of the target catalyst material on the surface of the nickel foam substrate and improve the interfacial bonding strength between the catalyst and the substrate, as well as subsequent catalytic performance, the nickel foam substrate needs to undergo the following activation pretreatment: 1) Base cutting and trimming: Cut the nickel foam raw material into rectangular blanks with a specification of 5cm×10cm. Use grinding to trim the cut edges, remove edge burrs and irregular protrusions, and ensure that the blank size is compatible with the inner cavity size of the subsequent liquid phase reaction vessel.

[0041] 2) Multi-step ultrasonic cleaning and activation: (1) Pickling solution ultrasonic removal: The trimmed foamed nickel blank is placed in a 3mol / L hydrochloric acid solution and ultrasonically treated for 30 minutes under ultrasonic power of 100W and ultrasonic frequency of 40kHz to remove the oxide film and attached metal impurity particles on the substrate surface. (2) Alcohol cleaning and degreasing: Take out the acid-treated foamed nickel blank, rinse it with deionized water 3 times, and then transfer it to anhydrous ethanol. Clean it with ultrasonic parameters for 30 minutes to remove oil and residual acid from the substrate surface. (3) Water washing and alcohol removal: The foamed nickel blank that has been washed with alcohol is transferred to deionized water again and ultrasonically cleaned for 30 minutes while maintaining the above ultrasonic parameters to completely remove the residual ethanol on the substrate surface and avoid introducing impurities into the subsequent reaction system.

[0042] 3) Vacuum drying treatment: The cleaned nickel foam substrate was placed in a vacuum drying oven and vacuum dried at room temperature for 2 hours. After drying, it was sealed for later use. Vacuum drying at room temperature can effectively avoid the problem of secondary oxidation of the substrate surface caused by high temperature drying and ensure the activation effect of the substrate.

[0043] 2. Core synthesis steps (microwave-driven one-step in-situ growth) 1) Preparation of precursor solution: Weigh 40 mmol Ni(NO3)2 6H2O dissolved in 200 mL of isopropanol, 20 mmol Fe(SO4)2 9H₂O was dissolved in 100 mL of deionized water (for rapid dissolution and to prevent oxidation). The two solutions were then quickly mixed, and 10 mmol of CTAB (hexadecyltrimethylammonium bromide) was added as a cationic surfactant, primarily acting as a structure-directing agent. After sonication for 1 min, a turbid (with noticeably small particles) dark green solution was formed.

[0044] 2) Substrate immersion: Immerse the pretreated nickel foam completely in the above precursor solution to ensure that the nickel foam is fully wetted by the solution (immersion time is 5 minutes to avoid local areas not in contact with the reaction solution).

[0045] 3) Microwave Reaction: Transfer the beaker containing the precursor solution and nickel foam to a custom-made microwave reaction vessel (high borosilicate glass, 500 mL volume), with a sealable opening. Set the microwave reactor parameters: power 2000 W, reaction temperature 60℃, reaction time 30 minutes (microwaves are the core driving force, directly influencing nucleation and crystal growth, not auxiliary heating). After the reaction, turn off the microwave reactor and allow the vessel to cool naturally to room temperature (approximately 10 minutes).

[0046] 3. Post-processing steps: Washing: Remove the foamed nickel (the surface has formed a light green Ni2Fe(SO4)). 0.5 (OH)6(H2O) 3.85 The nanosheet array was first rinsed 5 times with deionized water, and then rinsed 3 times with anhydrous ethanol to remove unreacted precursors and byproducts adsorbed on the surface.

[0047] Vacuum drying: The cleaned nickel foam was placed in a vacuum drying oven and dried overnight (12 hours) at 60°C to obtain the final product "microwave-synthesized Ni2Fe(SO4)". 0.5 (OH)6(H2O) 3.85 / NF catalyst.

[0048] Figure 1 Microwave synthesis of Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 X-ray diffraction (XRD) pattern of the catalyst. Comparison of the sample diffraction curve with the standard PDF card (PDF#01-077-4367) of the target product shows that the characteristic diffraction peaks at 2θ≈10°, 17°, 23°, 32°, and 38° are highly consistent with the standard peak positions, confirming that the layered hydroxide derivative of the target composition can be successfully synthesized under mild conditions of microwave irradiation at 60℃ for 30 min. Meanwhile, the diffraction peaks exhibit significant broadening, indicating that the product has a partially crystalline structure—this structure retains the stability of the layered framework while introducing abundant active sites due to lattice defects, laying the structural foundation for subsequent improvement of electrocatalytic performance.

[0049] Figure 2 The Ni2Fe(SO4) prepared in Example 1 0.5 (OH)6(H2O) 3.85Scanning electron microscopy (SEM) images (magnification × 18.0k) of the / NF catalyst clearly show a continuous array of nanosheets on the catalyst surface: the sheets are nanometer-thick and interwoven to form a porous three-dimensional network. This morphology offers significant advantages: firstly, the thin nanosheet structure greatly increases the catalyst's specific surface area, exposing more active sites to the electrolyte; secondly, the porous network accelerates mass transport and oxygen desorption during the reaction, effectively optimizing the kinetic efficiency of the electrocatalytic oxygen evolution reaction (OER). This result establishes a good structure-property correlation with the partial crystalline structure revealed by XRD, further validating the precise control of product morphology by this synthetic method.

[0050] Figure 3 The image shows the microwave synthesis of Ni2Fe(SO4) according to the present invention. 0.5 (OH)6(H2O) 3.85 A schematic diagram of the "one-step liquid-phase microwave method" process used for the / NF catalyst. The left module shows the microwave reaction equipment and the built-in reaction system. The microwave field serves as the core energy source for nucleation and crystal growth, replacing the traditional heating method to dominate the reaction process and avoiding the problems of low energy utilization and slow reaction rate in the auxiliary heating mode. The three-necked flask in the middle is the reaction vessel, and the light green mixed liquid inside corresponds to the precursor system. The right side clearly shows the key parameters and raw material composition of the process: the reaction is continuously microwave irradiated at 60°C for 30 min. The precursor adopts a dual-solvent dispersion system. The Ni source (nickel nitrate) is dissolved in isopropanol and the Fe source (ferrous sulfate) is dissolved in deionized water. At the same time, an appropriate amount of CTAB is introduced as a morphology regulator. Finally, the in-situ growth of the catalyst is achieved using pretreated nickel foam as a substrate.

[0051] This process, through an integrated design of "dual solvent dispersion - microwave in-situ growth," solves the problem of Fe... 2+ The problems of easy oxidation and uneven dispersion of precursors have been addressed by leveraging the rapid and uniform heating characteristics of microwaves to achieve one-step efficient synthesis of catalysts on large-size substrates, effectively ensuring the morphological uniformity and structural controllability of the products.

[0052] Figure 4 This is the Ni2Fe(SO4) prepared in Example 1 of this invention. 0.5 (OH)6(H2O) 3.85 The image shows the physical appearance of the / NF catalyst. As can be seen from the image, the catalyst is uniformly covered on the surface of the large-sized nickel foam substrate. The overall morphology is dense and uniformly distributed, exhibiting a regular light green color. There are no uneven phenomena such as local color differences or agglomeration. This clearly demonstrates the excellent controllability of this synthesis process in terms of product morphology consistency.

[0053] The Ni2Fe(SO4) prepared in this invention 0.5 (OH)6(H2O) 3.85 The / NF catalyst was based on a large-size nickel foam substrate measuring 5 cm × 10 cm. To verify the uniformity of the catalyst's performance, six independent test regions (corresponding to Regions 1-6 marked in the figure) were uniformly selected on its surface, and the electrochemical performance of the oxygen evolution reaction (OER) was tested in each region to obtain the current density-potential polarization curves for each region. The electrolyte used for the OER reaction was 1 M KOH alkaline desalinated water.

[0054] exist Figure 5 As can be seen from the polarization curves on the right, the curves corresponding to the six regions have a very high degree of overlap. Within the potential range of 1.2–1.6 V (vs RHE), the current density variation trends in each region are basically consistent, with no significant differences. This result fully demonstrates that the large-size catalyst synthesized by this method exhibits highly uniform electrochemical performance in different regions. This reflects both the stability and controllability of the synthesis process and proves that the structure and performance of the product have good consistency, meeting the batch uniformity requirements for industrial-grade catalysts.

[0055] Example 2 Unlike Example 1, the parameters for the microwave reaction were: power 2000 W, reaction temperature 60°C, and reaction time 10 min.

[0056] Example 3 Unlike Example 1, the parameters for the microwave reaction were: power 2000 W, reaction temperature 60°C, and reaction time 50 min.

[0057] Example 4 Unlike Example 1, the parameters for the microwave reaction were: power 2000 W, reaction temperature 40°C, and reaction time 30 min.

[0058] Example 5 Unlike Example 1, the parameters for the microwave reaction were: power 2000 W, reaction temperature 80°C, and reaction time 30 min.

[0059] Example 6 Unlike Example 1, the parameters for the microwave reaction were: power 2000 W, reaction temperature 100℃, and reaction time 30 min.

[0060] Figure 9 To illustrate the effect of different reaction times on catalyst performance during microwave synthesis. Figure 10This study investigates the effect of different reaction temperatures on catalyst performance during microwave synthesis. In exploring different reaction conditions, the electrolyte used in the OER reaction was 1M KOH alkaline water.

[0061] This invention uses an isopropanol-water mixed solution as the reaction medium, with a boiling point of 80℃-90℃. Due to the limitations of the medium, if the synthesis temperature is higher than its boiling point, isopropanol will become unstable due to the destruction of system stability, making it impossible to achieve controllable growth of the target material. If the temperature is too low, the kinetics of precursor nucleation and crystal growth are insufficient, making it difficult to form a layered structure with catalytic activity. Combining the electrochemical performance curves (parameter group of 40-100℃), this process determines the appropriate temperature range by matching the boiling point characteristics of the medium, ensuring the synergistic controllability of material structure and performance.

[0062] Regarding the reaction time, based on the LSV curves (parameter groups of 10, 30, and 50 min), it can be seen that: when the reaction time is too short (e.g., 10 min), the precursor does not complete sufficient nucleation and growth, and a complete catalytically active structure cannot be formed; after the reaction time reaches 30 min, the material has completed effective growth, and the catalytic performance reaches the ideal level; further extending to 50 min does not significantly improve performance. Therefore, 30 min was selected as the reaction time, which significantly shortens the process cycle and reduces time costs while ensuring that the material performance meets the standards, thus meeting the efficiency and economic requirements of industrial mass production.

[0063] Comparative Example 1 Unlike Example 1, microwave synthesis was not used; instead, a long-term immersion at room temperature for 24 hours was employed.

[0064] 1. The activation pretreatment process of the nickel foam substrate is the same as that in Example 1.

[0065] 2. Core synthesis steps: 1) The preparation of the precursor solution is the same as in Example 1.

[0066] 2) Substrate immersion: The pretreated nickel foam is completely immersed in the above precursor solution for 24 hours.

[0067] 3. The post-processing steps are the same as in Example 1.

[0068] Figure 7Linear sweep voltammetry performance comparison curves of the catalyst prepared by microwave synthesis in Example 1 of the present invention and the catalyst prepared by long-term room-temperature impregnation in Comparative Example 1 for the oxygen evolution reaction. Among them, the electrolyte for the oxygen evolution reaction is 1M KOH alkaline fresh water. As can be seen from the figure: it intuitively presents the differences in the electrocatalytic performance of the catalyst in Example 1 of the present invention and the catalyst material prepared in Comparative Example 1. In the low current density range (corresponding voltage 1.2 - 1.5 V vs. RHE), the current density of the sample in Example 1 is better, indicating that in the low-power consumption scenario driven by low voltage, this sample can initiate the oxygen evolution reaction with lower energy consumption and maintain stable catalysis. This characteristic is highly suitable for low-production-demand scenarios such as distributed small hydrogen production devices and hydrogen production for new energy microgrids, and can effectively reduce the operating energy consumption and equipment adaptation cost in such scenarios, reflecting the precise adaptation of the structure design of this sample to low-power conditions. In the high current density range, although the sample in Example 1 is slightly lower than the catalyst prepared in Comparative Example 1, the performance gap between the two is relatively limited; combined with its unique advantage in the low current region, the catalyst prepared in Example 1 actually has the characteristic of "differentiated scenario adaptation". Subsequently, only by finely adjusting the microstructure of the material can the performance in the high current region be further optimized. The excellent performance at the current low current density has fully demonstrated its application potential and the rationality of the structure design in the segmented scenario.

[0069] Figure 8 is the comparison of the electrochemical corrosion resistance of the catalyst prepared by microwave synthesis in Example 1 of the present invention and the catalyst prepared by long-term room-temperature impregnation in Comparative Example 1. Among them, the electrolyte in this test condition is 1M KOH alkaline seawater. Figure 8 is the corrosion polarization curve of the materials prepared by different preparation methods, which intuitively reflects the differences in the electrochemical corrosion resistance of the two materials. The core index in the figure is the corrosion potential (Ecorr). The corrosion potential of the catalyst prepared in Example allows

[0070] Corrosion potential is a key parameter for measuring the corrosion resistance of materials. A higher corrosion potential means a higher driving potential is required for the material to undergo a corrosion reaction. This implies that under the same electrochemical conditions (such as an alkaline system for water electrolysis, specifically 1 mol / L alkaline seawater), this sample is more difficult to corrode and exhibits stronger corrosion resistance. For water electrolysis catalysts, long-term exposure to a strong electrochemical corrosion environment directly determines the material's service life. The catalyst prepared in Example 1 has a higher corrosion potential, which can effectively delay the dissolution of active components and structural collapse during electrolysis. It can maintain more stable catalytic performance during long-term continuous operation. This characteristic is particularly suitable for industrial-grade hydrogen electrolysis and other scenarios requiring long-term service, fully demonstrating the advantages of the catalyst prepared in this embodiment in terms of structural stability design.

[0071] Comparative Example 2 Unlike Example 1, CTAB was not added.

[0072] Figure 11 The figures show a comparison of the morphology of the catalyst with and without the addition of CTAB; (a) represents the catalyst without CTAB, and (b) represents the catalyst with CTAB. As can be seen from the figures, without CTAB, the material exists as discrete particulate aggregates, unevenly distributed on the surface of the nickel foam substrate, with obvious local accumulation. This is because, in the absence of a structure-directing agent, the nucleation and growth processes of the material become uncontrolled, easily forming irregular aggregates, which not only leads to uneven exposure of active sites but also weakens the interfacial bonding with the substrate. After the addition of CTAB, the material transforms into a continuous and uniform thin-layer structure, completely and densely coating the surface of the nickel foam substrate, without obvious agglomeration or accumulation. This is because CTAB, as a cationic surfactant, guides the material to uniformly nucleate and grow along the substrate surface through a template effect formed by self-assembly, achieving precise morphology control.

[0073] Figure 12 This figure compares the effect of CTAB addition on the oxygen evolution reaction (OER) of the prepared catalyst. The electrolyte used for the OER reaction was alkaline fresh water containing 1M KOH. The sample with CTAB added (purple curve) shows a significantly higher current density at the same voltage than the sample without CTAB (blue curve), indicating superior OER catalytic activity and achieving a higher OER rate with lower energy consumption. Without CTAB, the material exhibits discrete particle agglomerates (corresponding to SEM morphology), resulting in low and uneven exposure of active sites and hindering electrolyte mass transfer and charge transport. The addition of CTAB, however, creates a continuous and uniform thin-layer structure (corresponding to SEM morphology), ensuring sufficient and uniform exposure of active sites and optimizing charge transport pathways and electrolyte wetting, ultimately leading to superior electrocatalytic performance.

[0074] Test 1: Application of electrolysis of alkaline desalination: A three-electrode system was used for seawater electrolysis testing: the material synthesized in Example 1 was used as the working electrode (anode), the Hg / HgO electrode as the reference electrode, and the carbon rod as the counter electrode; the electrodes were placed in an alkaline freshwater electrolyte, such as... Figure 6 As shown, under external circuit conditions, at 1 A / cm 2 Constant current electrolysis was performed at a current density, and the test results showed that the system could operate stably for more than 4000 hours.

[0075] Figure 6 It is Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 Electrochemical stability test curves of the / NF catalyst during the oxygen evolution reaction (OER). This test used 1 M KOH alkaline fresh water as the electrolyte system and employed an industrial-grade high current density (1 A). cm -2 The long-term stability of the catalyst was verified under the operating conditions.

[0076] The curve trend shows that during continuous operation at room temperature for 4000 hours, the potential of the catalyst remained within a stable range, with only minor normal fluctuations and no significant potential rise or performance degradation. This test result fully demonstrates that the catalyst prepared in this invention possesses extremely excellent long-term stability under high current density conditions, can withstand continuous electrolysis operation for extended periods, and fully meets the stringent durability requirements for catalysts in industrial-grade freshwater electrolysis hydrogen production scenarios.

[0077] Test 2: Application of electrolysis of alkaline seawater: A three-electrode system was used for seawater electrolysis testing: the material synthesized in Example 1 was used as the working electrode (anode), the Hg / HgO electrode as the reference electrode, and the carbon rod as the counter electrode; the electrodes were placed in an alkaline seawater electrolyte, such as... Figure 13 As shown, under external circuit conditions, at 1 A / cm 2 Constant current electrolysis was performed at a current density, and the test results showed that the system could operate stably for more than 3000 hours.

[0078] The "alkaline seawater" electrolyte is prepared by using filtered natural seawater instead of traditional deionized water as the solvent to obtain an alkaline seawater electrolyte with a KOH concentration of 1 mol / L. That is, solid KOH is directly dissolved in the filtered seawater to achieve a KOH molar concentration of 1 mol / L, rather than adding additional KOH to the seawater.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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. Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 A process for the preparation of a catalyst of the type Ni2Fe(SO4)2(OH)6(H2O) characterized in that, The microwave synthesis comprises the following steps: The nickel salt and the iron salt are dissolved in solvents, mixed, and then a cationic surfactant is added to obtain a precursor solution; The pretreated nickel foam is immersed in the precursor solution and placed in a microwave reaction container for microwave reaction; The microwave reaction is performed at a temperature of 40-100℃ for 10-60 minutes.

2. The production method according to claim 1, characterized by, The iron salt is a sulfate salt, and the nickel salt is a nitrate salt.

3. The preparation method according to claim 1, characterized in that, The nickel salt is dissolved in a first solvent, which comprises isopropyl alcohol; the amount ratio of the nickel salt to the first solvent is (30-50 mmol):(150-250 mL), preferably (35-45 mmol):(180-220 mL); Preferably, the iron salt is dissolved in a second solvent, which comprises water; the amount ratio of the iron salt to the second solvent is (10-30 mmol):(50-150 mL), preferably (15-25 mmol):(80-120 mL).

4. The preparation method according to claim 1, characterized in that, The molar ratio of the nickel salt, the iron salt, and the cationic surfactant is (30-50):(10-30):(5-15), preferably (35-45):(15-25):(8-12); Preferably, the cationic surfactant comprises cetyltrimethylammonium bromide; Preferably, the pretreated nickel foam is completely immersed in the precursor solution for 2-10 minutes. Preferably, the microwave reaction container is made of high borosilicate material and is an open and sealable container.

5. The preparation method according to claim 1, characterized in that, The microwave reaction power is 1000-3000 W, preferably 1500-2500 W. Preferably, the microwave reaction temperature is 50-70℃, and the reaction time is 20-40 minutes. Preferably, after the microwave reaction, the method further comprises rinsing and drying; preferably, the rinsing comprises multiple rinsing with water and anhydrous ethanol in sequence; and preferably, the drying comprises vacuum drying.

6. A Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 / NF catalyst characterized in that, Prepared by the method of any one of claims 1-5.

7. The catalyst of claim 6, wherein The catalyst surface presents a continuous nanosheet array structure: the sheet thickness is in the nanometer level, and the nanosheets are interwoven to form a porous three-dimensional network. Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 The foam nickel substrate surface is uniformly covered, and the overall morphology is dense and uniformly distributed.

8. Ni2Fe(S04) (OH)6(H20) prepared by the process of any one of claims 1 to 5. 0.5 (OH)6(H20) 3.85 / NF catalyst or the Ni2Fe(S04) (OH)6(H20) catalyst of claim 6 or 7 for use in the electrolysis of water, preferably seawater. 0.5 (OH)6(H20) 3.85 / NF catalyst or the Ni2Fe(S04) (OH)6(H20) catalyst of claim 6 or 7 for use in the electrolysis of water, preferably seawater.

9. A method of producing hydrogen by electrolysis of water, characterized by, The method comprises the following steps: Ni2Fe(SO4) prepared by the preparation method of any one of claims 1-5 0.5 (OH)6(H2O) 3.85 / NF catalyst or the Ni2Fe(SO4) of claim 6 or 7 0.5 (OH)6(H2O) 3.85 / NF catalyst as a working electrode to electrolyze water; The electrolyte comprises fresh water, seawater, alkaline fresh water, or alkaline seawater.

10. An electrolytic cell characterized by, comprising an anode, a cathode and an electrolyte, the anode comprising Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 / NF catalyst or Ni2Fe(SO4) 0.5 (OH)6(H2O) 3.85 / NF catalyst, the electrolyte comprising fresh water, seawater, alkaline fresh water or alkaline seawater.

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