A water oxidation catalyst, its preparation method and application

Abstract

The application belongs to the technical field of hydrogen production by water electrolysis, and particularly relates to a water oxidation catalyst and a preparation method and application thereof. The application utilizes the hydrolysis of metal cations in a hydrolysable metal salt solution to produce a weakly acidic heterogeneous soaking system, slowly acts on the surface of a metal substrate, and etches the surface of the metal substrate while removing the surface metal oxides; the etched metal ions and the hydrolyzed metal ions are combined on the surface of the substrate to form an LDH catalyst structure, ensuring high catalytic activity; meanwhile, under the action of interface confinement, a dense transition layer structure is slowly formed at the interface between the metal substrate and the catalyst layer. The transition layer, as a bridge between the metal substrate and the catalyst layer, has the same structure as the LDH, but the morphology is denser, and the transition layer fully covers the surface of the metal substrate, thereby firmly anchoring the LDH catalyst structure layer on the surface of the metal substrate, so that the OER catalyst has high activity and high stability under the condition of an industrial current density.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410131060.0, filed on January 30, 2024, entitled "A water oxidation catalyst and its preparation method and application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of water electrolysis for hydrogen production technology, specifically relating to a water oxidation catalyst, its preparation method, and its application. Background Technology

[0004] Hydrogen is a clean fuel with high energy density, wide availability, no pollution, and storability. Compared to hydrogen production from traditional fossil fuels (such as coal and oil) (gray hydrogen) and natural gas (blue hydrogen), hydrogen production through water electrolysis using renewable energy sources (such as solar, wind, and nuclear power) (green hydrogen) has advantages such as wide availability of raw materials, zero carbon emissions, and renewability. Existing industrial-scale low-temperature water electrolysis hydrogen production technologies mainly include alkaline electrolyzer (AWE) and proton exchange membrane electrolysis (PEM-WE). AWE has low material costs, high stability, and is easy to scale up industrially, but it suffers from hydrogen-oxygen cross-contamination problems, low operating efficiency, and corrosion issues when using high concentrations of alkalinity. PEM-WE has a compact structure, high hydrogen production efficiency, and short response time, but it has high investment costs, cannot escape dependence on precious metals (such as Pt), and has limited hydrogen production capacity. In recent years, the newly developed anion exchange membrane electrolysis (AEM-WE) combines the advantages of both AWE and PEM-WE, namely low material cost, compact structure, and high hydrogen production efficiency, possessing enormous potential for hydrogen production through water electrolysis. However, AEM-WE is still some distance from large-scale industrial production of green hydrogen, mainly because it cannot operate at industrial-grade current densities (e.g., ≥1000 mA cm⁻¹). -2 It still faces the problem of not being able to achieve both hydrogen production performance and stability.

[0005] The core components of the water electrolysis for hydrogen production are the water oxidation (OER) catalyst and the hydrogen reduction (HER) catalyst. Among these, the OER catalytic process, involving four-electron transfer, exhibits slow reaction kinetics and is more restrictive of the entire water electrolysis process than the HER process. Therefore, developing efficient and stable OER catalysts is particularly important for green hydrogen engineering. Existing studies have shown that noble metal compounds, such as IrO2 and RuO2, demonstrate excellent water oxidation activity, but their high cost limits their widespread adoption. Therefore, the development of non-noble metal OER catalysts is gradually becoming a research trend. However, current reports on non-noble metal OER catalysts focus more on improving catalytic performance and less on long-term stability (e.g., >8000 h), especially stability under industrial-grade current density conditions and high-performance conditions.

[0006] Therefore, there is an urgent need to develop a preparation method that can firmly fix the catalyst structure on the surface of a metal substrate in order to meet the requirements of stable and efficient operation of OER reaction at industrial-grade current density. Summary of the Invention

[0007] Therefore, the technical problem to be solved by this application is to overcome the above-mentioned defects of water oxidation catalysts in the existing water electrolysis hydrogen production process, thereby providing a water oxidation catalyst, its preparation method and application.

[0008] Therefore, this application provides the following technical solution:

[0009] This application provides a method for preparing a water oxidation catalyst, comprising the following steps:

[0010] S1, Prepare a hydrolyzable metal salt solution and adjust the pH of the hydrolyzable metal salt solution to 2.5-6.5;

[0011] S2, the metal substrate is soaked in a hydrolyzable metal salt solution;

[0012] S3. Add an organic solvent to the system from step S2 to form a heterogeneous system and react for 4-72 h.

[0013] Optionally, in step S1, the concentration of the hydrolyzable metal salt solution is 20-400 mmol / L.

[0014] Optionally, the hydrolyzable metal salt includes, but is not limited to, at least one of nickel chloride, nickel sulfate, nickel nitrate, ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, vanadium trichloride, vanadium oxysulfate, aluminum chloride, indium trichloride, cerium trichloride, cerium sulfate, and bismuth trichloride.

[0015] Optionally, in step S2, the soaking temperature is 5-50 ℃ and the soaking time is 0-5 h;

[0016] Alternatively, the soaking time is 1-2 hours.

[0017] Optionally, in step S3, the organic solvent includes, but is not limited to, at least one of acetone, methanol, ethanol, propanol, isopropanol, allyl alcohol, butanol, 2-butanol, tert-butanol, ethylene glycol, propylene glycol, tetrahydrofuran, dimethyl ether, ethyl acetate, and N,N-dimethylformamide.

[0018] And / or, the volume ratio of the organic solvent to the hydrolyzable salt solution is in the range of (0.5-9):1;

[0019] And / or, the metal substrate includes, but is not limited to, at least one of nickel foam, iron foam, nickel-iron foam, nickel mesh, iron mesh, nickel-iron mesh, nickel felt, iron felt, nickel-iron felt, nickel electrode plate, and iron electrode plate. If the metal substrate contains only one metal element, the metal element in the hydrolyzable metal salt solution must be different from the metal composition in the substrate in order to subsequently form a layered bimetallic compound (LDH).

[0020] Optionally, the reaction temperature in step S3 is 20-60 °C, and the reaction time is 10-72 h.

[0021] This application also provides a water oxidation catalyst prepared by the above-described preparation method.

[0022] This application also provides an application of the above-mentioned water oxidation catalyst in the electrolysis of water to produce hydrogen.

[0023] Optionally, the current density for hydrogen production via water electrolysis is 500-4000 mA cm⁻¹. -2 This application is particularly suitable for industrial-grade current densities of 1000-4000 mA cm⁻¹. -2 Hydrogen production by electrolysis of water.

[0024] Optionally, it is applicable to the electrolysis of alkaline water systems. The alkaline water systems include, but are not limited to, alkaline water, alkaline seawater, and alkaline mineral water.

[0025] This application provides a water oxidation catalyst, which includes a metal substrate and a catalyst layer. A transition layer is also attached to the surface of the metal substrate between the metal substrate and the catalyst layer. The catalyst layer and the transition layer have the same lamellar structure, and the morphology of the transition layer is denser than that of the catalyst layer.

[0026] It should be noted that the "lamellar structure" in this application refers to the fact that the main structure of the catalyst layer and the transition layer is a lamellar structure. In the transition layer, these lamellar structures are tightly packed together, and in the catalyst layer, these lamellar structures can form more delicate structures such as petal-shaped, honeycomb-shaped, cluster-shaped, and bundle-shaped.

[0027] It should also be noted that "dense" means that the lamellar structure has a smaller area and a higher density of lamellar structure arrangement.

[0028] It should also be noted that the smaller the gap between the transition layer and the metal substrate, the more suitable the water oxidation catalyst is for stable and efficient operation at industrial-grade current densities. This is because the water oxidation catalyst of this application achieves stable and efficient operation at industrial-grade current densities by including a dense transition layer. This dense transition layer firmly anchors the catalyst layer to the surface of the metal substrate, meaning the presence of the transition layer gives the water oxidation catalyst good mechanical stability, thus enabling it to withstand higher industrial-grade current densities. Therefore, the smaller the gap between the transition layer and the metal substrate, the stronger the bond between the catalyst and the metal substrate, and the more stable and efficient the water oxidation catalyst can operate at industrial-grade current densities.

[0029] In some embodiments, there is no gap between the substrate and the transition layer at most locations, wherein most locations are more than 80% of the locations.

[0030] Optionally, the thickness of the transition layer is 0.2-4 μm;

[0031] Optionally, the thickness of the transition layer is 0.2-3 μm;

[0032] Optionally, the thickness of the transition layer is 1-3 μm;

[0033] Optionally, the thickness of the transition layer is 2-3 μm.

[0034] It should be noted that the thickness of the transition layer in the water oxidation catalyst is not completely uniform at every location in this application; some areas are thicker than others. The thickness of the transition layer in the water oxidation catalyst is related to the position of the metal reaction sites in the metal substrate. For example, when the metal substrate is nickel foam, because nickel foam has a honeycomb structure, the nickel reaction sites in the nickel foam are oriented in various directions. When the orientation of the nickel reaction sites in the nickel foam is in the same direction as gravity, because the hydrolyzable salt solution is above the metal substrate, the reaction contact area of ​​the nickel reaction sites in this direction is smaller, the etching rate of these nickel reaction sites is slower, and the catalyst layer formed at these locations is thinner, thus the transition layer thickness is smaller. Conversely, when the orientation of the nickel reaction sites in the nickel foam is opposite to gravity, the transition layer thickness is greater.

[0035] It should also be noted that the thickness of the transition layer refers to the thickness range at most locations of the transition layer. For example, the thickness of the transition layer refers to the range consisting of at least 50% of the locations where the transition layer is located, and in most cases, it refers to the range consisting of at least 60% of the locations where the transition layer is located. That is, the thickness range at most locations of the transition layer can usually be taken as the thickness of the transition layer, but this does not exclude the possibility that the thickness at individual locations is lower or higher than the thickness range of the transition layer.

[0036] It should be noted that the method for measuring the thickness of the transition layer in the water oxidation catalyst of this application includes the following steps:

[0037] S11, Obtain a cross-sectional scanning electron microscope image (SEM image) of the water oxidation catalyst to be tested (using... Figure 19 (For example, to illustrate)

[0038] S12, as Figure 23 As shown, the boundary line 4 between the metal substrate 3 and the transition layer 2 is determined based on the location where the morphology and structure of the metal substrate 3 and the transition layer 2 change significantly, and the boundary line 5 between the catalyst layer 1 and the transition layer 2 is determined based on the location where the density of the lamellar structure changes significantly.

[0039] S13. Based on the boundary line 4, the trend line 6 is given. Along the vertical direction of the trend line at the position to be measured, the distance between the trend line 6 and the boundary line 5 is measured, which is the thickness of the transition layer at the position to be measured. Figure 24 This is another schematic diagram of the transition layer thickness test in the water oxidation catalyst. For the part that deviates significantly from the trend line in the figure (the part circled in the figure), it will be discarded in the process of determining the trend line 6 based on the boundary line 4.

[0040] S14. Select several different locations and measure the thickness according to the method in step S13. The range consisting of the thickness at at least 50% of the locations is the thickness of the water oxidation catalyst transition layer.

[0041] Optionally, the metal substrate includes at least one of the following: nickel foam, iron foam, nickel-iron foam, nickel mesh, iron mesh, nickel-iron mesh, nickel felt, iron felt, nickel-iron felt, nickel electrode plate, and iron electrode plate.

[0042] And / or, the catalyst layer and the transition layer are both composed of layered bimetallic compounds.

[0043] Optionally, the metal substrate is nickel foam or iron foam;

[0044] The catalyst layer and transition layer are composed of at least one of nickel-iron layered bimetallic compounds, nickel-vanadium layered bimetallic compounds, nickel-aluminum layered bimetallic compounds, and nickel-cerium layered bimetallic compounds.

[0045] The reaction principle of this application is as follows:

[0046] In step S1, the metal salt undergoes a hydrolysis reaction in water, generating a large number of hydrogen ions. In steps S2 and S3, these hydrogen ions come into contact with the metal substrate, initially etching away the loose metal oxides on the surface; as time progresses, they also slowly etch away some of the surface metal. Besides cleaning the metal substrate surface, the etching process also releases a certain amount of substrate metal ions (such as Ni). 2+ Fe 2+ Fe 3+ These released ions can serve as raw materials for the subsequent formation of layered bimetallic compounds (LDH). This mild etching method avoids the environmental pollution, structural damage to the metal substrate, and low utilization of the metal ion source that may be caused by conventional acid etching of metal substrates. The etched metal ions can be used as raw materials for the formation of LDH catalysts in subsequent heterogeneous systems; while the ions participating in the hydrolysis reaction are usually metal ions with higher valence states (such as +3 valence), they can also participate in the subsequent formation process of LDH catalysts while completing the hydrolysis reaction.

[0047] Due to the different solubilities of metal compounds in water and organic solvents, the addition of organic solvents in S3 leads to the precipitation of a large number of nanoparticles. These nanoparticles are uniformly dispersed in the liquid phase and easily adsorb onto the surface of metal substrates (such as nickel foam), thereby reducing the adsorption energy of the metal surface. Due to the acidic characteristics of the liquid system (caused by the hydrolysis of metal ions), acid etching of the metal substrate surface continues, resulting in a significant increase in the concentration of metal ions at the solid-liquid interface. These etched ions and metal ions in the liquid gradually grow the LDH catalytic structure with the nanoparticles adsorbed on the metal surface as the core (or seed). As the catalytic structure grows slowly, the metal substrate surface is gradually covered, and acid etching gradually weakens (the rate slows down, but it is still occurring). At this point, metal ions are only enriched at the interface between the metal substrate surface and the catalytic structure. Under the effect of interface confinement, a dense transition layer gradually forms at the interface over time (with low growth kinetics). When the transition layer completely covers the metal substrate, the etching process stops, the concentration of surrounding metal ions decreases, the catalytic structure and the transition layer stop growing, and the catalyst growth process ends. Since the growth of the transition layer is accompanied by the etching of the metal surface on the substrate, the metal surface is completely covered by the transition layer when the catalyst growth stops. Due to the presence of the dense transition layer, the LDH catalyst layer with a good three-dimensional structure is firmly anchored to the metal substrate surface. The catalyst obtained in this application exhibits both high OER activity and high stability under industrial-grade current density conditions. Furthermore, due to the complete coverage of the metal substrate surface by the transition layer, the metal substrate can be effectively protected from harmful ions (such as Cl). - The erosion of (etc.) allows the catalyst to be used not only for hydrogen production from alkaline water, but also for hydrogen production from alkaline seawater and alkaline mineral water.

[0048] The technical solution of this application has the following advantages:

[0049] The method for preparing the water oxidation catalyst provided in this application includes the following steps: S1, preparing a hydrolyzable metal salt solution and adjusting the pH of the hydrolyzable metal salt solution to 2.5-6.5; S2, immersing a metal substrate in the hydrolyzable metal salt solution; S3, adding an organic solvent to the system in step S2 to form a heterogeneous system, and reacting for 4-72 h. This application utilizes the hydrolysis of metal cations in the hydrolyzable metal salt solution to create a weakly acidic heterogeneous immersion system, which slowly acts on the surface of a metal substrate (such as foamed nickel, foamed iron, etc.), removing surface metal oxides while partially etching the surface of the metal substrate; these etched metal ions combine with hydrolyzed metal ions on the substrate surface to form an LDH catalyst structure, ensuring its high catalytic activity; simultaneously, under the effect of interface confinement, a dense transition layer structure slowly forms at the interface between the metal substrate and the catalyst layer (with low growth kinetics). This transition layer, acting as a bridge between the metal substrate and the catalyst layer, has the same structure as LDH but a denser morphology and fully covers the surface of the metal substrate, thus achieving a firm anchoring of the LDH catalytic structure layer on the metal substrate surface. The resulting 3D self-supporting catalyst outer layer (catalyst layer) is responsible for high OER activity, the metal substrate is responsible for support and electron transport, and the dense intermediate transition layer is responsible for firmly anchoring the catalyst layer to the metal substrate surface, thereby achieving high activity and high stability of OER water oxidation catalysis under industrial-grade current density conditions. In addition, this application utilizes the weak acid effect of cation hydrolysis to etch the surface of the metal substrate (without adding or only adding a very small amount of acid to adjust the pH value), avoiding the environmental pollution that may be caused by conventional acid washing methods; the cations etched from the metal substrate surface participate in the formation of the catalyst layer, avoiding the need for an external substrate metal ion source, saving costs; this method has low raw material costs, mild processing conditions, simple operation, high repeatability, high OER activity, strong OER stability, and is easy to scale up for large-scale application.

[0050] The method for preparing the water oxidation catalyst provided in this application can improve the thickness of the transition layer by further optimizing the reaction time, which can further improve the operational stability of the catalyst at industrial-grade current densities.

[0051] The water oxidation catalyst provided in this application comprises a metal substrate, a catalyst layer, and a transition layer attached to the surface of the metal substrate between the metal substrate and the catalyst layer. Both the catalyst layer and the transition layer have a layered structure, and the morphology of the transition layer is more dense than that of the catalyst layer. The surface of the metal substrate of the water oxidation catalyst is completely covered by the transition layer. Due to the presence of the transition layer, and the fact that the catalyst layer and the transition layer have the same layered structure, the LDH catalyst layer with a good three-dimensional structure can be firmly anchored to the surface of the metal substrate. Because the morphology of the transition layer is more dense than that of the catalyst layer, this hierarchical structure allows the catalyst to be distributed deeply on the surface of the metal substrate, which is beneficial to the mass transfer process during catalysis and is responsible for providing high OER activity. The metal substrate is responsible for support and electron transport. The catalyst obtained in this application has both high OER activity and high stability under industrial-grade current density conditions. Furthermore, because the transition layer completely covers the surface of the metal substrate, it can effectively protect the metal substrate from harmful ions (such as Cl). - The catalyst is protected against corrosion by various factors, including alkaline water hydrogen production, seawater hydrogen production, and alkaline mineral water hydrogen production. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0053] Figure 1 This is a spherical aberration electron microscope (STEM) image of nanoparticles in the heterogeneous system formed in Example 1;

[0054] Figure 2 This is a scanning electron microscope (SEM) image of the catalyst on the surface of the nickel foam substrate obtained in Example 1;

[0055] Figure 3 This is a diagram illustrating the growth process of the LDH catalyst layer and the dense transition layer on the surface of the nickel foam substrate in Example 2.

[0056] Figure 4 This is a photograph of the large-size (20 cm × 20 cm) nickel foam substrate catalyst provided in Example 3;

[0057] Figure 5 Here are the catalyst homogenization distribution diagrams obtained in Example 4: (a) a 5 cm × 5 cm catalyst photograph, (b) a comparison of linear scan performance curves at different points (25 ℃, 1 M KOH).

[0058] Figure 6 This is the stability curve of the nickel foam catalyst in 1 M KOH electrolyte (25 °C, 1000 mA cm⁻¹) in Example 4. -2 );

[0059] Figure 7 The linear sweep performance curves (25 °C) of the foamed nickel-based catalyst obtained in Example 4 in alkaline simulated seawater containing 1 M KOH and real seawater are shown.

[0060] Figure 8 The stability curve of the foamed nickel-based catalyst obtained in Example 4 in an alkaline seawater electrolyte containing 1 M KOH (25 °C, 1000 mA cm⁻¹) is shown. -2 );

[0061] Figure 9 This is a cross-sectional scanning electron microscope (SEM) image of the foamed iron-based catalyst obtained in Example 8;

[0062] Figure 10 This is a scanning electron microscope (SEM) image of the surface of the foamed iron-based catalyst obtained in Example 8;

[0063] Figure 11 The linear sweep performance curve of the foamed iron-based catalyst obtained in Example 8 (25 °C, 1 M KOH).

[0064] Figure 12 The linear sweep performance curve of the catalyst obtained in Example 10 (25 °C, 1 M KOH).

[0065] Figure 13 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Comparative Example 1;

[0066] Figure 14 Stability curves of the catalyst obtained in Comparative Example 1 in 1 M KOH electrolyte (25 °C, 1000 mAcm) -2 );

[0067] Figure 15 The stability curve of the catalyst obtained in Comparative Example 1 in an alkaline seawater electrolyte of 1 M KOH (25 °C, 1000 mA cm⁻¹) is shown. -2 );

[0068] Figure 16 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Comparative Example 3;

[0069] Figure 17 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Comparative Example 5;

[0070] Figure 18 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Example 3;

[0071] Figure 19 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Example 4;

[0072] Figure 20 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Example 5;

[0073] Figure 21 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Example 7;

[0074] Figure 22 This is a cross-sectional scanning electron microscope (SEM) image of the catalyst obtained in Example 9;

[0075] Figure 23 This is a schematic diagram of the transition layer thickness test in a water oxidation catalyst;

[0076] Figure 24 This is another schematic diagram of the transition layer thickness test in a water oxidation catalyst;

[0077] Figure label:

[0078] 1. Catalyst layer; 2. Transition layer; 3. Metal substrate; 4. Boundary line; 5. Dividing line; 6. Trend line. Detailed Implementation

[0079] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0080] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0081] It should be noted that in this embodiment, the metal substrate, transition layer, and catalyst layer are distinguished by SEM images of the cross-section of the water oxidation catalyst. In the cross-sectional SEM image, the metal substrate is located at the bottom of the image, and its morphology is significantly different from the sheet-like morphology of the transition layer and catalyst layer. The transition layer is located between the catalyst layer and the metal substrate. The location where the morphological structure changes significantly is used as the boundary between the transition layer and the metal substrate. For example, when the metal substrate is foamed nickel, it can be seen that the metal substrate has a porous structure, and the transition layer has a sheet-like structure. The location where the density of the sheet-like morphology changes significantly is used as the boundary between the transition layer and the catalyst layer. In the following embodiments and comparative examples, the thickness of the transition layer refers to the range of thickness at locations where the transition layer exceeds 50%, determined based on the thickness of the transition layer measured at multiple different locations in the SEM images.

[0082] Example 1

[0083] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0084] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous chloride metal salt in water, stir to form a solution with a metal ion concentration of 100 mol / L, and adjust the pH to 3.5 with sulfuric acid;

[0085] S2: Oxide etching on the surface of the metal substrate: Immerse the foamed nickel (Suzhou Christie's, 80 ppi, the same below, size 2 cm × 2 cm) in the weakly acidic solution S1 and let it stand at 30 ℃ for 4 h;

[0086] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring, wherein the volume ratio of ethanol to ferrous chloride solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 40 °C for 24 h, then rinsed with water and dried.

[0087] The term "heterogeneous liquid system" refers to a liquid system (suspension, emulsion) containing insoluble solid particles (including nano- or micron-sized particles). Heterogeneous liquid systems are formed by utilizing the differences in solubility of inorganic metal salts in different solvents. For example, FeCl2 is soluble in water but insoluble in ethanol. Therefore, when ethanol is added to an aqueous solution of FeCl2 under stirring, many uniform but insoluble particles are produced, forming a heterogeneous liquid system.

[0088] Figure 1The TEM image of the insoluble nanoparticles in the liquid phase system after adding ethanol in step S3 of this embodiment shows that these nanoparticles are in an amorphous state and have a uniform size distribution (nanometer scale). These particles are very easy to adsorb onto the surface of the metal substrate in the liquid phase environment to reduce its surface energy, and thus act as a core (or seed) to bypass the nucleation process that is originally required for the formation and growth of the new LDH phase, thereby assisting in the rapid formation of the LDH structure. Figure 2 The image shows an SEM image of the catalyst obtained in this embodiment. As can be seen from the image, the catalyst is mainly composed of tightly packed sheets at the bottom (i.e., the transition layer) and an upper secondary sheet structure (catalyst layer). This multi-level structure allows the catalyst to be distributed deep within the surface of the metal substrate, which is beneficial to the mass transfer process during catalysis.

[0089] In Example 1, a transition layer with a thickness of 1-2 μm was formed in the S3 system. The resulting catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 M KOH) under alkaline conditions, and the system was able to operate stably for more than 4500 hours.

[0090] Example 2

[0091] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0092] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous chloride metal salt in water, stir to form a solution with a metal ion concentration of 200 mol / L, and adjust the pH to 3.5 with hydrochloric acid;

[0093] S2: Oxide etching on the surface of the metal substrate: Immerse 8 pieces of nickel foam (2 cm × 2 cm in size) in S1 weak acid solution and let stand at 30 ℃ for 4 h;

[0094] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring conditions, wherein the volume ratio of ethanol to ferrous chloride solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 25 °C, and one piece was taken out at 1 h, 2 h, 4 h, 8 h, 16 h, 24 h, 36 h and 72 h, respectively. After being taken out, the pieces were rinsed with water and dried.

[0095] Figure 3The image shows a cross-sectional SEM image of the catalyst obtained in this embodiment. As can be seen, a distinct lamellar structure (catalyst layer) is obtained after immersion in the S3 system for 1 h. The lamellar structure grows larger with increasing time. When the immersion time in step S3 reaches 4 h or more, a dense transition layer is formed between the catalyst layer and the nickel foam substrate (the area between the dashed lines in the image represents the transition layer; the hydrophobic lamellar structure above the dashed lines is the catalyst layer, and the area below the dashed lines is the metal substrate without a lamellar structure). The thickness is approximately 0.2-0.5 μm, and it gradually increases with time (0.5-0.8 μm for 8 h immersion, 1-2 μm for 16 h, and 1.5-2.5 μm for 24 h). However, when the time is extended to 36 h or more, the thickness of the transition layer no longer increases, eventually remaining at 2-3 μm. The catalyst obtained after 36 h of reaction was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 M KOH) under alkaline conditions, and it was found to operate stably for more than 6800 h.

[0096] Example 3

[0097] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0098] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous chloride metal salt in water, stir to form a solution with a metal ion concentration of 30 mol / L, and adjust the pH to 6.5 with hydrochloric acid;

[0099] S2: Oxide etching on the surface of the metal substrate: Immerse the nickel foam (20 cm × 20 cm in size) in the weakly acidic solution S1 and let it stand at 5 °C for 0.1 h;

[0100] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring, wherein the volume ratio of ethanol to ferrous chloride solution was 0.5:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 20 °C for 6 h, then rinsed with water and dried.

[0101] like Figure 4 As shown, the obtained catalyst grows well on the surface of the nickel foam substrate, indicating that even under relatively low growth conditions (such as low metal ion concentration, high pH value and short soaking time), the catalyst can still be grown relatively uniformly on a large-sized (20 cm × 20 cm) metal foam surface.

[0102] from Figure 5It can be seen that in this embodiment, even with a large metal substrate size, the potential difference at different points is extremely small. This indicates that the performance difference across different locations in the water oxidation catalyst prepared in this embodiment is small. Therefore, in actual industrial use, the catalytic effect is similar across the water oxidation catalyst, and the effective reaction area of ​​the water oxidation catalyst is very close to the surface area of ​​the catalyst itself. This means that in actual industrial use, the proportion of the water oxidation catalyst participating in the reaction is extremely high, which can significantly improve industrial production efficiency. In Example 3, a transition layer is generated in the S3 system, such as... Figure 18 As shown, the transition layer thickness is 0.2–0.3 μm. The obtained catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 M KOH) at a certain temperature, and it was found to operate stably for more than 1500 hours.

[0103] In this method, the metal substrate can be replaced with a larger metal electrode plate, which allows a transition layer and a catalyst layer to grow on the surface of the metal electrode plate, thereby protecting the metal electrode plate and preventing its corrosion.

[0104] Example 4

[0105] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0106] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous chloride metal salt in water, stir to form a solution with a metal ion concentration of 400 mol / L, and adjust the pH to 2.6 with hydrochloric acid;

[0107] S2: Oxide etching on the surface of the metal substrate: Immerse the nickel foam (5 cm × 5 cm) in the weakly acidic solution S1 and let it stand at 50 ℃ for 5 h;

[0108] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring, wherein the volume ratio of ethanol to ferrous chloride solution was 8:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 60 °C for 70 h, then rinsed with water and dried.

[0109] In Example 4, a transition layer is generated in the S3 system, such as... Figure 19 As shown, the thickness of the transition layer is 3-4 μm.

[0110] like Figure 5 As shown, the obtained catalyst grows more uniformly on the nickel foam surface, and the linear scan curves measured at at least three locations on it almost overlap, indicating that the catalyst has uniform catalytic activity at multiple sites. The obtained catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability test of oxidation in alkaline water (1 M KOH), such as Figure 6 As shown, no significant increase in potential was observed during the testing period exceeding 8760 hours (one year), indicating that the material possesses excellent catalytic stability in alkaline water. The catalyst was used to simulate alkaline seawater and in real alkaline seawater electrolysis for hydrogen production, such as... Figure 7 As shown, in simulated seawater (chloride ion concentration consistent with seawater) with 1 M KOH + 0.5 M NaCl and in real seawater with 1 M KOH, the catalyst exhibits excellent catalytic activity at 1000 mA cm⁻¹. -2 The overpotentials at these values ​​were 203 mV and 218 mV, respectively, exceeding most existing reports. When applied to real alkaline seawater electrolysis, at 1000 mA cm⁻¹... -2 It can operate stably for more than 2000 hours at industrial-grade current densities (see...). Figure 8 Based on its stable operating trend, it is expected to achieve a stable operating time similar to that of alkaline water. The excellent stability of seawater electrolysis mainly stems from two aspects: First, the dense transition layer completely coats the metal substrate, protecting it from corrosive chloride ions; second, the catalyst LDH structure has anion exchange capacity, which, after absorbing some chloride ions, can act as a like ion to repel more chloride ions in seawater, thus protecting the catalyst.

[0111] Example 5

[0112] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0113] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable vanadium trichloride metal salt in water, stir to form a solution with a concentration of 200 mol / L, and adjust the pH to 3.5 with sulfuric acid;

[0114] S2: Oxide etching on the surface of the metal substrate: Immerse the nickel foam (2 cm × 2 cm) in the weakly acidic solution S1 and let it stand at 30 ℃ for 4 h;

[0115] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring, wherein the volume ratio of ethanol to vanadium trichloride solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 40 °C for 24 h, then rinsed with water and dried.

[0116] In Example 5, a transition layer is generated in the S3 system, such as... Figure 20 As shown, the transition layer thickness is 0.5-1 μm. The obtained catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2Stability testing under alkaline real seawater oxidation (containing 1 M KOH, 25 °C) showed that the catalyst could operate stably for 1200 h. The obtained catalyst was then used in industrial-grade current density (1000 mA cm⁻¹). -2 The stability test of alkaline water oxidation (1 M KOH) showed that it could run stably for more than 2100 h.

[0117] Example 6

[0118] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0119] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable aluminum chloride metal salt in water, stir to form a solution with a concentration of 200 mol / L, and adjust the pH to 3.5 with sulfuric acid;

[0120] S2: Oxide etching on the surface of the metal substrate: Immerse the nickel foam (2 cm × 2 cm) in the weakly acidic solution S1 and let it stand at 30 ℃ for 4 h;

[0121] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring conditions, wherein the volume ratio of ethanol to aluminum chloride solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 40 °C for 24 h, then rinsed with water and dried.

[0122] In Example 6, a transition layer with a thickness of 0.2-0.5 μm was formed in the S3 system. The resulting catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 The catalyst was tested for stability under alkaline real seawater oxidation (containing 1 M KOH, 25 °C) and operated stably for 1000 h. The obtained catalyst was then used in industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 MKOH) at a lower temperature, and the system was able to operate stably for more than 1200 h.

[0123] Example 7

[0124] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0125] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable cerium sulfate metal salt in water, stir to form a solution with a concentration of 200 mol / L, and adjust the pH to 3.5 with sulfuric acid;

[0126] S2: Oxide etching on the surface of the metal substrate: Immerse the nickel foam (2 cm × 2 cm) in the weakly acidic solution S1 and let it stand at 30 ℃ for 4 h;

[0127] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring, wherein the volume ratio of ethanol to cerium sulfate solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 40 °C for 24 h, then rinsed with water and dried.

[0128] In Example 7, a transition layer is generated in the S3 system, such as... Figure 21 As shown, the transition layer thickness is 1-2 μm. The obtained catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 The catalyst was tested for stability under alkaline real seawater oxidation (containing 1 M KOH, 25 °C) and operated stably for 1000 h. The obtained catalyst was then used in industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 M KOH) at a certain temperature, and it was found to operate stably for more than 3200 h.

[0129] Example 8

[0130] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0131] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous sulfate and nickel nitrate metal salts in water, stir to form a solution with a concentration of 200 mol / L, the molar ratio of iron to nickel is 1:3.5, and adjust the pH to 3.5 with sulfuric acid;

[0132] S2: Oxide etching on the surface of the metal substrate: Immerse the foamed iron (2 cm × 2 cm) in the weakly acidic solution S1 and let it stand at 30 ℃ for 4 h;

[0133] S3: In-situ growth of the catalyst: Ethanol was slowly added to the S2 system under ultrasonic stirring conditions, wherein the volume ratio of ethanol to ferrous sulfate and nickel nitrate solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 40 °C for 24 h, then rinsed with water and dried.

[0134] In Example 8, a transition layer with a thickness of 1-2 μm is generated in the S3 system. Figure 9 As shown in the cross-sectional SEM image, the obtained catalyst contains a three-layer structure: an upper lamellar structure, a middle transition layer structure, and a bottom foamed iron structure. Figure 10 As shown in the top-view SEM image, the water oxidation catalyst is also composed of a tightly packed layer at the bottom (transition layer) and a large petal-shaped secondary layer structure (catalyst layer). Linear sweep curve testing was performed on it, as shown... Figure 11 As shown, at 1000 mA cm -2 The overpotential is 240 mV.

[0135] The resulting catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the alkaline real seawater oxidation (containing 1 MKOH, 25 °C), and the catalyst operated stably for 1500 h. The obtained catalyst was then used in industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 M KOH) at a certain temperature, and it was found to operate stably for more than 2500 hours.

[0136] Example 9

[0137] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0138] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous sulfate metal salt in water, stir to form a solution with a concentration of 200 mol / L, and adjust the pH to 3.5 with sulfuric acid;

[0139] S2: Oxide etching on the surface of the metal substrate: Immerse the nickel foam (2 cm × 2 cm) in the weakly acidic solution S1 and let it stand at 30 ℃ for 4 h;

[0140] S3: In-situ growth of the catalyst: Isopropanol was slowly added to the S2 system under ultrasonic stirring, wherein the volume ratio of isopropanol to ferrous sulfate solution was 3:1, forming a heterogeneous liquid phase system. The system was allowed to stand at 40 °C for 24 h, then rinsed with water and dried.

[0141] In Example 9, a transition layer is generated in the S3 system, such as... Figure 22 As shown, the transition layer thickness is 2-3 μm. The obtained catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability testing under alkaline real seawater oxidation (containing 1 M KOH, 25 °C) showed that the catalyst could operate stably for 1800 h. The obtained catalyst was then used in industrial-grade current density (1000 mA cm⁻¹). -2 Stability tests were conducted on the oxidation of alkaline water (1 M KOH) at a certain temperature, and it was found to operate stably for more than 5500 hours.

[0142] Example 10

[0143] This embodiment provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0144] S1: Preparation of weakly acidic hydrolysis solution: Dissolve a certain amount of easily hydrolyzable ferrous sulfate metal salt in water, stir to form a solution with a concentration of 200 mol / L, and adjust the pH to 3.5 with sulfuric acid;

[0145] S2: In-situ growth of catalyst: Under ultrasonic stirring, ethanol was slowly added to the S1 system, wherein the volume ratio of ethanol to ferrous sulfate solution was 3:1, forming a heterogeneous liquid phase system that immerses the metal substrate. Nickel foam (2 cm × 2 cm) was immersed in it and allowed to stand at 40°C for 36 h. After being removed, it was rinsed with water and dried.

[0146] In Example 10, a transition layer with a thickness of 0.5-1.5 μm was formed in the S3 system. The obtained catalyst was subjected to linear sweep spectroscopy testing in an alkaline aqueous electrolyte of 1 M KOH (25 °C). Figure 12 As shown, at 1000 mA cm -2 The overpotential is 225 mV. The obtained catalyst was used at an industrial-grade current density (1000 mA cm⁻¹). -2 Stability test of alkaline water oxidation (1 M KOH) showed that it can operate stably for more than 2500 h.

[0147] Comparative Example 1

[0148] This comparative example provides a water oxidation catalyst, the preparation steps and operating parameters of which are as follows:

[0149] S1: Pickling pretreatment of foamed metal: Place the foamed nickel (2 cm × 2 cm) into 2 M hydrochloric acid and ultrasonically wash for 30 min, then clean it in sequence with anhydrous ethanol, acetone and deionized water.

[0150] S2: Preparation of metal salt suspension: Nickel nitrate is dissolved in ethanol, and ferrous sulfate is dissolved in deionized water. The volume ratio of ethanol to water is 2:1. After thorough mixing, a metal salt suspension is formed with a metal ion concentration of 200 mol / L.

[0151] S3: In-situ growth of catalyst: The pretreated foam metal is immersed in a metal salt suspension and soaked at 30°C for 24 h. After being taken out, it is rinsed repeatedly with anhydrous ethanol and deionized water 2-5 times and dried for later use.

[0152] In step S2 of this comparative example, a metal ion source required for LDH structure growth was added, enabling rapid growth of the catalytic layer; however, the pH value of the system was not adjusted, resulting in almost no or only weak etching of the metal substrate surface, making it impossible to form a transition layer under interfacial confinement. Figure 13 As shown, the catalyst layer structure of the comparative catalyst is similar to that of the catalyst layer obtained in this application, consisting of a multi-level sheet structure, but no obvious transition layer was found, and there are a small number of gaps between the catalyst layer and the metal substrate.

[0153] The stability of the obtained catalyst was tested in an alkaline aqueous electrolyte of 1 M KOH (25 °C). Figure 14As shown, at 1000 mA cm -2 The potential increased by about 400 mV over approximately 1000 h, indicating that the catalytic activity gradually decreased over time.

[0154] The stability of the obtained catalyst was tested in an alkaline seawater electrolyte of 1 M KOH (25 °C). Figure 15 As shown, at 1000 mA cm -2 The potential increase was about 1000 mV after about 5 hours, indicating that the catalyst could hardly operate stably in alkaline seawater.

[0155] Comparative Example 2

[0156] This comparative example provides a water oxidation catalyst, which differs from Example 2 only in that the reaction time in step S3 is 2 h.

[0157] The obtained catalyst was tested in an alkaline seawater electrolyte of 1 M KOH (25 °C, 1000 mA cm⁻¹). -2 After running stably for 3 hours, the potential rises rapidly. Figure 3 It is known that a catalyst growth time of 2 hours is insufficient to produce a transition layer. Therefore, although the catalyst has a large number of catalytic sheet structures, it cannot be used in alkaline seawater due to the lack of protection from the transition layer.

[0158] Comparative Example 3

[0159] This comparative example provides a water oxidation catalyst, which differs from Example 1 only in that no organic solvent is added in step S3.

[0160] The obtained catalyst was tested in an alkaline seawater electrolyte of 1 M KOH (25 °C, 1000 mA cm⁻¹). -2 After running stably for about 3 hours, the potential rises rapidly. The main role of the organic solvent is to induce the generation of nanoparticles, while in aqueous solutions lacking nanoparticles, the resulting catalyst transition layer is not significant (e.g., Figure 16 As shown in the figure, it does not have the function of stabilizing catalysis in alkaline seawater.

[0161] Comparative Example 4

[0162] This comparative example provides a water oxidation catalyst, which differs from Example 1 only in that it uses a non-hydrolyzable metal salt, NaCl.

[0163] The resulting catalyst surface showed almost no visible catalyst structure adhesion, and in an alkaline seawater electrolyte of 1 M KOH (25 °C, 1000 mA cm⁻¹), it was successfully tested. -2The stable operation time was less than 1 hour. This indicates that non-hydrolyzable metal salts cannot meet the requirements for etching the metal substrate and generating the catalyst structure, making them unsuitable for use in seawater electrolysis for hydrogen production.

[0164] Comparative Example 5

[0165] This comparative example provides a water oxidation catalyst, which differs from Example 1 only in that step S1 does not include the step of adjusting pH.

[0166] The resulting catalyst has a small sheet structure with an overall thickness of only 1-2 μm. Although a dense transition layer can be observed, there is significant delamination between the transition layer and the nickel foam substrate. The transition layer is not tightly adhered to the metal substrate, therefore the catalyst layer cannot be firmly anchored to the surface of the metal substrate (see [link to relevant documentation]). Figure 17 This may be related to the high pH of the soaking system. The stability of the obtained catalyst was tested in an alkaline aqueous electrolyte of 1 M KOH (25 °C) at 1000 mAcm⁻¹. -2 The potential increase is approximately 300 mV over about 500 hours; while in an alkaline seawater electrolyte of 1 M KOH (25 °C, 1000 mAcm⁻¹), the potential rise is only about 300 mV. -2 After 5 hours of stable operation, the potential rose rapidly. This indicates that adjusting the mother liquor to a reasonable pH range is crucial for the etching of the metal substrate and the formation of the catalyst. Without a suitable weakly acidic mother liquor environment, the formation of the catalyst (morphology, structure, and adhesion to the substrate) is inhibited to varying degrees, which is detrimental to its stable electrocatalysis in alkaline water and alkaline seawater.

[0167] To facilitate data comparison, some parameters and test results of the water oxidation catalysts provided in the examples and comparative examples are summarized below:

[0168] Table 1

[0169]

[0170] Note: " / " in the table indicates that the test was not performed.

[0171] The test data in the table above show that increasing the thickness of the transition layer can significantly improve the stable operating time of the catalyst. This may be because the transition layer can play a certain role in corrosion prevention, thereby extending the service life of the catalyst. The comparison between the examples and the comparative examples shows that the transition layer is tightly attached to the surface of the metal substrate, which can firmly anchor the catalyst layer to the surface of the metal substrate and significantly extend the stable operating time of the catalyst. If the thickness of the transition layer is almost zero or the transition layer is not tightly attached to the metal substrate, the adhesion of the catalyst layer on the metal substrate is very unstable, and it cannot play a role in corrosion prevention. It can hardly operate stably in alkaline real seawater.

[0172] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for preparing a water oxidation catalyst, characterized in that, Includes the following steps: S1, prepare a hydrolyzable metal salt solution and adjust the pH of the hydrolyzable metal salt solution to 2.5-6.5; the hydrolyzable metal salt includes at least one of nickel chloride, nickel sulfate, nickel nitrate, ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, vanadium trichloride, vanadium oxysulfate, aluminum chloride, indium trichloride, cerium trichloride, cerium sulfate, and bismuth trichloride; S2, the metal substrate is soaked in a hydrolyzable metal salt solution; the metal substrate is nickel foam or iron foam. S3. Add an organic solvent to the system from step S2 to form a heterogeneous system and react for 4-72 h.

2. The method for preparing the water oxidation catalyst according to claim 1, characterized in that, In step S1, the concentration of the hydrolyzable metal salt solution is 20-400 mmol / L.

3. The method for preparing the water oxidation catalyst according to claim 1, characterized in that, In step S2, the soaking temperature is 5-50 ℃ and the soaking time is 0-5 h.

4. The method for preparing the water oxidation catalyst according to claim 1, characterized in that, In step S2, the soaking time is 1-2 hours.

5. The method for preparing the water oxidation catalyst according to claim 1, characterized in that, In step S3, the organic solvent includes at least one of acetone, methanol, ethanol, propanol, isopropanol, allyl alcohol, butanol, 2-butanol, tert-butanol, ethylene glycol, propylene glycol, tetrahydrofuran, dimethyl ether, ethyl acetate, and N,N-dimethylformamide.

6. The method for preparing the water oxidation catalyst according to claim 1, characterized in that, The volume ratio of the organic solvent to the hydrolyzable salt solution is in the range of (0.5-9):

1.

7. The method for preparing the water oxidation catalyst according to any one of claims 1-6, characterized in that, The reaction temperature in step S3 is 20-60 °C, and the reaction time is 10-72 h.

8. A water oxidation catalyst prepared by the preparation method according to any one of claims 1-7.

9. The application of the water oxidation catalyst according to claim 8 in the electrolysis of water to produce hydrogen.

10. The application according to claim 9, characterized in that, The current density for hydrogen production by water electrolysis is 500-4000 mA•cm. -2 .

11. The application according to claim 9 or 10, characterized in that, Suitable for electrolysis of alkaline water systems.

12. The application according to claim 11, characterized in that, The alkaline water system includes alkaline seawater or alkaline mineral water.

13. A water oxidation catalyst prepared by the preparation method according to any one of claims 1-7, characterized in that, The water oxidation catalyst includes a metal substrate and a catalyst layer. A transition layer is attached to the surface of the metal substrate between the metal substrate and the catalyst layer. The catalyst layer and the transition layer have the same lamellar structure, and the morphology of the transition layer is denser than that of the catalyst layer. The metal substrate is nickel foam or iron foam. Both the catalyst layer and the transition layer are composed of layered bimetallic compounds. The catalyst layer and the transition layer are composed of at least one of nickel-iron layered bimetallic compounds, nickel-vanadium layered bimetallic compounds, nickel-aluminum layered bimetallic compounds, and nickel-cerium layered bimetallic compounds.

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