Preparation method of self-supporting anode catalyst, catalyst and application thereof

Abstract

The invention provides a preparation method of a self-supporting anode catalyst, the catalyst and application of the catalyst, and relates to the technical field of electrolyzed water oxygen evolution catalysts.The method comprises the steps that a foamed ferronickel substrate is provided and pretreated; immersing the pretreated foamed ferronickel substrate into the first precursor solution for standing reaction, forming a transition metal sulfide layer on the surface of the substrate through in-situ growth, and washing and drying to obtain an intermediate product; and placing the intermediate product in a second precursor solution for hydrothermal reaction, and growing on the surface of the transition metal sulfide layer to form a layered double hydroxide catalyst layer, thereby obtaining the self-supporting anode catalyst with a three-layer structure of layered double hydroxide, transition metal oxide and foamed ferronickel. According to the invention, the problems of weak binding force between a non-noble metal anode catalyst layer and a substrate and poor stability under high current density can be effectively solved, so that high-activity, high-stability and long-life oxygen evolution reaction in an alkaline or anion exchange membrane electrolysis water system can be realized.

Description

Technical Field

[0001] This invention relates to the field of oxygen evolution catalyst technology for water electrolysis, specifically to a method for preparing a self-supporting anode catalyst, the catalyst itself, and its applications. Background Technology

[0002] Electrolysis of water to produce hydrogen is one of the key technologies for realizing the industrialization of green hydrogen energy. The oxygen evolution reaction at the anode is a bottleneck restricting overall efficiency, and the core of this bottleneck lies in a high-performance, low-cost, and stable anode catalyst. Currently, research and applications mainly focus on two types of materials: one is noble metal catalysts, represented by ruthenium and iridium, which have excellent activity and stability, but their high cost and scarcity limit large-scale industrial applications; the other is non-noble metal catalysts, represented by nickel-iron layered double hydroxides, which have attracted much attention due to their low cost and good activity, and are considered a potential alternative.

[0003] However, existing non-precious metal catalysts, represented by nickel-iron layered double hydroxides, are usually grown directly on foamed metal substrates, which has the following obvious technical drawbacks:

[0004] First, the physical bond between the catalyst layer and the substrate is weak. Under prolonged or high-current-density operating conditions, the catalyst layer is prone to peeling off and detaching from the substrate, leading to electrode structure damage and rapid activity decay. Second, the material system itself has limited conductivity, and its structure is unstable under high-current-density conditions, resulting in its catalytic activity and long-term operational stability under high-current-density conditions falling far short of the requirements for industrial applications. Summary of the Invention

[0005] To address at least some of the technical problems in related technologies, this invention provides a method for preparing a self-supporting anode catalyst, the catalyst itself, and its applications. This invention uses inexpensive nickel-iron foam as a substrate, and adds [a specific chemical compound] between it and NiFe-LDH. Intercalation enhances the bonding between the catalyst layer and the substrate. The preparation of the intermediate intercalation layer is carried out at room temperature and pressure, which facilitates experimental scale-up. In this invention... The addition of intercalation enhances catalytic activity and conductivity, and exhibits excellent performance under high current density conditions, enabling stable testing over long periods and at high currents.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes:

[0007] According to a first aspect of the present invention, a method for preparing a self-supporting anode catalyst is provided, comprising the following steps:

[0008] Step S1: Provide and pre-treat the foamed nickel-iron substrate;

[0009] Step S2: Immerse the pretreated foamed nickel-iron substrate in the first precursor solution and allow it to react statically. A transition metal sulfide layer is formed in situ on the substrate surface. After washing and drying, the intermediate product is obtained.

[0010] Step S3: The intermediate product is placed in the second precursor solution for hydrothermal reaction to grow a layered double hydroxide catalyst layer on the surface of the transition metal sulfide layer, thereby obtaining a self-supporting anode catalyst with a three-layer structure of layered double hydroxide, transition metal oxide, and foamed nickel iron.

[0011] The first precursor solution contains nickel salt, iron salt and sulfur source; the second precursor solution contains nickel salt, iron salt, urea and ammonium fluoride.

[0012] Optionally, in step S1, the ratio of nickel to iron in the foamed nickel-iron substrate is 1:1; the pretreatment specifically includes: placing the foamed nickel-iron substrate in an acid solution for ultrasonic cleaning to remove the surface oxide layer, and then washing it with water and ethanol in sequence and drying it.

[0013] Optionally, the acid solution is a 1 mole per liter hydrochloric acid solution, and the ultrasonic cleaning time is 25 to 35 minutes.

[0014] Optionally, in step S2, the nickel salt in the first precursor solution is nickel chloride hexahydrate, the iron salt is ferric chloride nonahydrate, and the sulfur source is sodium thiosulfate pentahydrate; the static reaction is carried out at room temperature and pressure for 14 to 16 hours.

[0015] Optionally, in step S3, the nickel salt in the second precursor solution is nickel nitrate hexahydrate, and the iron salt is ferric nitrate hexahydrate; the hydrothermal reaction is carried out at a temperature of 100°C to 120°C for 4 hours.

[0016] Optionally, the transition metal sulfide layer formed in step S2 is transformed into a nickel-iron oxide intercalation layer during the subsequent hydrothermal reaction.

[0017] According to a second aspect of the present invention, a self-supporting anode catalyst is also provided, which is prepared by the preparation method described in any of the technical solutions of the first aspect of the present invention. Its structure is a self-supporting three-layer composite structure, which consists of, from the outside to the inside: a nickel-iron substrate-like double hydroxide catalyst layer, a nickel-iron oxide intercalation layer, and a foamed nickel-iron substrate.

[0018] Optionally, the nickel-iron-based double hydroxide catalyst layer has a nanosphere microstructure formed by interlacing nanosheets.

[0019] According to a third aspect of the present invention, the application of the self-supporting anode catalyst described in any of the technical solutions of the second aspect of the present invention in the oxygen evolution reaction of water electrolysis is also provided.

[0020] Optionally, it can be specifically applied to the anodic oxygen evolution reaction in alkaline or anion exchange membrane water electrolysis systems.

[0021] Beneficial effects:

[0022] 1. Through the above technical solution, firstly, the method of the present invention can achieve in-situ construction and strong bonding of the structure. Specifically, the method of the present invention, through the sequential operation of "substrate pretreatment → static reaction of the first precursor solution → hydrothermal reaction of the second precursor solution", enables the transition metal sulfide intermediate layer and the nickel-iron base layer crystalline double hydroxide catalyst layer to grow sequentially and in-situ on the foamed nickel-iron substrate. This stepwise in-situ growth process ensures that the layers are not simply physically attached, but rather form a tight bond at the interface through chemical action. In this way, the key defects of poor bonding between the catalyst layer and the substrate and easy detachment in existing related technologies can be effectively solved, laying a technological foundation for the long-term structural stability of the electrode.

[0023] Second, the method of this invention enables the acquisition of composite structures with optimized performance. Specifically, the three-layer structure ultimately obtained by the method of this invention is a functionally integrated whole. The intermediate transition metal sulfide layer (after subsequent treatment) not only acts as a "binder" to enhance bonding within the structure, but also constitutes an interface layer that facilitates charge transport. Compared with a single "catalyst layer / substrate" binary structure, the three-layer structure of this invention optimizes its internal interface and electron transport characteristics, thereby providing structural possibilities for improving the electrocatalytic activity (such as reducing overpotential) and conductivity of the final product.

[0024] Third, the method of the present invention mainly involves impregnation, standing and hydrothermal reaction, which are relatively mild (e.g., hydrothermal temperature 120°C) and do not involve extremely complex or harsh preparation environments. Thus, this relatively simple and step-by-step process design makes it easy to reproduce in the laboratory and has the potential feasibility for industrial-scale production.

[0025] 2. Other beneficial effects or advantages of the present invention will be described in detail in the specific embodiments. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] in:

[0028] Figure 1This is a schematic flowchart of the preparation method of a self-supporting anode catalyst provided in an exemplary embodiment of the present invention;

[0029] Figure 2 This is a schematic flowchart of the preparation method of a self-supporting anode catalyst provided by another exemplary embodiment of the present invention;

[0030] Figure 3 This is an exemplary embodiment of the NiFe-LDH / SEM image of cross-section of / NFF material;

[0031] Figure 4 This is an exemplary embodiment of the NiFe-LDH / SEM image of the surface of / NFF material;

[0032] Figure 5 This is a comparison chart of LSV activity provided by an exemplary embodiment of the present invention;

[0033] Figure 6 This is an exemplary embodiment of the NiFe-LDH / / NFF at 1.5 The figure shows the stability test results under the current density. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] Furthermore, the terms "comprising" and "having," and any variations thereof, used in the description of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include other steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices. It should also be noted that in embodiments of this invention, the words "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in embodiments of this invention should not be construed as preferred or advantageous over other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0037] To facilitate a clearer and more accurate understanding of the technical solutions of this invention by those skilled in the art, the existing related technologies and their technical problems will be described in more detail below.

[0038] The widespread application of anion exchange membrane electrolysis for hydrogen production is limited by key materials (anode catalysts). Ruthenium-based and iridium-based catalysts exhibit excellent catalytic activity and stability in the water oxidation reaction (OER), but their low crustal abundance and high cost severely restrict their industrial application. Non-precious metal catalysts, due to their low cost and ease of industrial production, have attracted widespread attention, particularly nickel-iron-based layered double hydroxides (e.g., NiFe-LDH), which have shown good catalytic activity and stability in OERs.

[0039] However, similar NiFe-LDH catalysts also have the following problems:

[0040] First, the structure is unstable. Under long-term and high-potential conditions, the bonding ability between the substrate and the effective catalyst layer is poor, and it is easy to fall off, resulting in poor cycle stability.

[0041] Second, performance degradation is significant under high current testing conditions. At high current densities, NiFe-LDH catalysts often exhibit problems such as activity degradation and bubble accumulation, failing to meet the requirements for long-term industrial operation.

[0042] Third, the conductivity is relatively limited. Since NiFe-LDH itself is a layered hydroxide, the conductivity within and between layers is low, and the electron and ion transport is not ideal.

[0043] In view of this, the present invention provides a novel solution: a method for preparing a self-supporting anode catalyst, the catalyst itself, and its applications. The technical concept of this invention lies in designing and constructing a three-layer integrated self-supporting structure of "catalytic layer-interface intercalation-conductive substrate," fundamentally solving the key bottleneck of weak bonding between the traditional non-precious metal catalyst layer and the substrate, and poor stability under high current. Specifically, firstly, a transition metal sulfide layer is grown in situ on a foamed nickel-iron substrate as an intermediate transition layer; subsequently, a nickel-iron base-based double hydroxide main catalytic layer is grown on its surface through a hydrothermal reaction, and the intermediate layer is transformed into a strongly bonded nickel-iron oxide intercalation layer during the process. In this way, the intermediate intercalation layer can be used as a "structural anchor" and "electron bridge," significantly enhancing the adhesion between the catalyst layer and the substrate through chemical bonding, preventing detachment, and improving the charge transport efficiency at the interface, thereby synergistically achieving excellent and stable oxygen evolution catalytic performance under high current density. This invention combines material design, interface engineering, and a simplified preparation process, providing a new and effective solution for developing high-performance, long-life non-precious metal anodes suitable for industrial water electrolysis for hydrogen production.

[0044] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0045] According to a first aspect of the invention, such as Figure 1 As shown, a method for preparing a self-supporting anode catalyst is provided, comprising the following steps:

[0046] Step S1: Provide and pre-treat the foamed nickel-iron substrate;

[0047] Step S2: Immerse the pretreated foamed nickel-iron substrate in the first precursor solution and allow it to react statically. A transition metal sulfide layer is formed in situ on the substrate surface. After washing and drying, the intermediate product is obtained.

[0048] Step S3: The intermediate product is placed in the second precursor solution for hydrothermal reaction to grow a layered double hydroxide catalyst layer on the surface of the transition metal sulfide layer, thereby obtaining a self-supporting anode catalyst with a three-layer structure of layered double hydroxide, transition metal oxide, and foamed nickel iron.

[0049] The first precursor solution contains nickel salt, iron salt and sulfur source; the second precursor solution contains nickel salt, iron salt, urea and ammonium fluoride.

[0050] Through the above technical solution, firstly, the method of the present invention can achieve in-situ construction and strong bonding of the structure. Specifically, the method of the present invention, through the sequential operation of "substrate pretreatment → static reaction of the first precursor solution → hydrothermal reaction of the second precursor solution", enables the transition metal sulfide intermediate layer and the nickel-iron base layer crystalline double hydroxide catalyst layer to grow sequentially and in-situ on the foamed nickel-iron substrate. This stepwise in-situ growth process ensures that the layers are not simply physically attached, but rather form a tight bond at the interface through chemical action. In this way, the key defects of poor bonding between the catalyst layer and the substrate and easy detachment in existing related technologies can be effectively solved, laying a technological foundation for the long-term structural stability of the electrode.

[0051] Second, the method of this invention enables the acquisition of composite structures with optimized performance. Specifically, the three-layer structure ultimately obtained by the method of this invention is a functionally integrated whole. The intermediate transition metal sulfide layer (after subsequent treatment) not only acts as a "binder" to enhance bonding within the structure, but also constitutes an interface layer that facilitates charge transport. Compared with a single "catalyst layer / substrate" binary structure, the three-layer structure of this invention optimizes its internal interface and electron transport characteristics, thereby providing structural possibilities for improving the electrocatalytic activity (such as reducing overpotential) and conductivity of the final product.

[0052] Third, the method of the present invention mainly involves impregnation, standing and hydrothermal reaction, which are relatively mild (e.g., hydrothermal temperature 120°C) and do not involve extremely complex or harsh preparation environments. Thus, this relatively simple and step-by-step process design makes it easy to reproduce in the laboratory and has the potential feasibility for industrial-scale production.

[0053] In one embodiment of the present invention, in step S1, the ratio of nickel to iron in the foamed nickel-iron substrate is 1:1; the pretreatment may specifically include: placing the foamed nickel-iron substrate in an acid solution for ultrasonic cleaning to remove the surface oxide layer, and then washing it with water and ethanol in sequence and drying it.

[0054] In this embodiment, the molar ratio of nickel to iron in the substrate is first set to 1:1. This specific ratio provides optimal chemical compositional matching for the nickel-iron-based intermediate layer and catalyst layer (NiFe-LDH) to be grown in subsequent steps. This matching provides more thermodynamically favorable conditions for the subsequent in-situ growth reaction, promoting tight bonding between layers at the atomic / ionic scale, thereby enhancing the interfacial bonding strength and overall structural uniformity of the final three-layer structure from the source. If the substrate ratio deviates from this value, it may affect the formation quality of the intermediate transition layer, thereby weakening the support and bonding effect on the catalyst layer.

[0055] Secondly, ultrasonic cleaning in an acidic solution (such as hydrochloric acid) to remove the surface oxide layer effectively removes the native oxide layer and contaminants from the substrate surface, exposing fresh, highly surface-active metal atoms. This effectively enhances the reactivity between the substrate and the first precursor solution, promoting in-situ growth. Simultaneously, sequential washing with water and ethanol followed by drying ensures a high degree of consistency in the initial state of the substrate (e.g., cleanliness, hydrophilicity) before each preparation. This consistency is an indispensable process control point for ensuring the stable and reproducible performance of each batch of catalyst in laboratory research and future industrial scale-up.

[0056] In one embodiment of the present invention, the acid solution is a hydrochloric acid solution with a concentration of 1 mole per liter, and the ultrasonic cleaning time is 25 to 35 minutes.

[0057] In this embodiment, firstly, regarding the selection of the concentration (1M), this concentration of hydrochloric acid solution is sufficient to effectively dissolve and remove various oxide layers (such as NiO, etc.) on the surface of the foamed nickel-iron substrate. This solution removes pollutants such as organic pollutants, providing a highly clean metal surface for subsequent reactions. Simultaneously, this concentration avoids excessive corrosion, structural damage, or uncontrollable changes in surface morphology of the substrate metal caused by using excessively strong acids, achieving a balance between effective cleaning and substrate protection.

[0058] Secondly, it should be noted that the lower limit of the ultrasonic cleaning time setting of 25 minutes is based on the minimum cleanliness requirement. If it is less than 25 minutes, the oxide layer on the substrate surface is easily not completely cleaned. The upper limit of the ultrasonic cleaning time setting of 35 minutes is based on the production efficiency requirement. If it exceeds 35 minutes, the acid is likely to cause excessive corrosion of the substrate material, resulting in low cleaning efficiency and energy waste.

[0059] Furthermore, the ultrasonic cleaning time can preferably be 30 minutes, which ensures the thoroughness and uniformity of the cleaning process. The cavitation effect of ultrasound enhances the penetration and mass transfer of acid in the complex three-dimensional porous structure of the substrate, enabling the effective removal of the oxide layer from the entire sample (not just the outer surface). This duration is sufficient to achieve effective cleaning while avoiding unnecessary energy and time consumption.

[0060] In one embodiment of the present invention, in step S2, the nickel salt in the first precursor solution is nickel chloride hexahydrate, the iron salt is ferric chloride nonahydrate, and the sulfur source is sodium thiosulfate pentahydrate; the static reaction is carried out at room temperature and pressure for 14 to 16 hours.

[0061] In this embodiment, nickel chloride hexahydrate and ferric chloride nonahydrate are first selected as the nickel and iron sources because these two salts have excellent solubility and can rapidly and completely dissociate in deionized water to form a homogeneous and clear precursor solution, thereby ensuring the uniformity of metal ion concentration in the solution. Sodium thiosulfate pentahydrate is selected as the sulfur source, which provides thiosulfate ions (… It exhibits specific reactivity in solution, enabling the in-situ and uniform nucleation and growth of nickel and iron sulfides on the substrate through a relatively mild chemical reaction (rather than simple precipitation) when in contact with the nickel-iron foam substrate. This specific combination of raw materials directly determines the specific chemical composition (Ni-Fe-S), structure, and morphology of the resulting intermediate layer, which is a crucial foundation for the successful and uniform growth of the LDH catalyst layer on it in subsequent hydrothermal steps.

[0062] Secondly, the mild reaction conditions (room temperature and pressure, 14 to 16 hours) not only make the operation extremely simple and energy consumption very low (no heating, pressurization, or stirring equipment is required; the pretreated substrate simply needs to be immersed in the solution and allowed to stand, greatly simplifying the operation process and reducing energy consumption and equipment requirements), but also facilitate uniform reaction and structure control (the mild standing conditions avoid problems such as excessively rapid deposition, unevenness, or loose structure that may result from vigorous reactions).

[0063] It should be noted that the lower limit of the settling time of 14 hours is based on the consideration of ensuring sufficient reaction. If it is less than 14 hours, the in-situ transition metal sulfide layer may not be fully covered, the thickness may be uneven, or the bonding may be weak. The upper limit of the settling time of 16 hours is based on the consideration of avoiding excessive reaction. Due to the acidic environment of metal ion hydrolysis, if it exceeds 16 hours, the acidic environment may excessively corrode the substrate material, thereby reducing the mechanical strength of the material and affecting the stability of the material in industrial chemical conditions.

[0064] Furthermore, the settling time can preferably be 15 hours. A 15-hour settling time is sufficient to allow the reaction to proceed fully, ensuring the formation of a dense, firmly bonded transition metal sulfide layer on the substrate surface, but without causing unnecessary side reactions or excessive growth due to excessive time. Moreover, tests have shown that samples obtained after a 15-hour settling period exhibit optimal performance, while excessively long settling times can negatively impact the material's mechanical strength.

[0065] In one embodiment of the present invention, in step S3, the nickel salt in the second precursor solution is nickel nitrate hexahydrate, and the iron salt is ferric nitrate hexahydrate; the hydrothermal reaction temperature is 100°C to 120°C, and the time is 4 hours.

[0066] In this embodiment, nickel nitrate hexahydrate and ferric nitrate hexahydrate are chosen as metal sources because nitrate ions have good chemical compatibility in a weakly alkaline hydrothermal environment. Their decomposition or reaction process is relatively mild, which is conducive to the formation of layered double hydroxides with moderate crystallinity and regular lamellar structure, rather than disordered hydroxide precipitates. The fixed hydration number (hexahydrate) of these two specific hydrated salts also means that their molecular weight is determined, which helps to make precise stoichiometric control when preparing the precursor solution, thereby ensuring the accuracy and consistency of the nickel-iron ratio in the final LDH catalyst layer. This is the chemical basis for obtaining stable and excellent catalytic activity.

[0067] Secondly, these hydrothermal conditions (120℃, 4 hours) allow for precise control of the catalyst layer growth. Specifically, the chosen temperature (120℃) provides sufficient thermal energy to drive processes such as metal ion hydrolysis, nucleation, and crystal growth, ensuring the formation of layered double hydroxides. Simultaneously, this is a relatively mild temperature, avoiding excessively high temperatures that could lead to coarse crystals, structural dehydration, or damage to the underlying structure. Regarding the chosen time (4 hours), this duration sets a reasonable cycle for crystal growth. It ensures the reaction proceeds fully, achieving sufficient thickness and coverage of the catalyst layer, while avoiding excessive growth, agglomeration, or adverse phase transitions that could occur with prolonged periods.

[0068] It should be noted that if the hydrothermal conditions are set below 100℃ or the hydrothermal duration is less than 4 hours, LDH may not form a complete phase; if the hydrothermal conditions are set above 120℃ or the hydrothermal duration is greater than 4 hours, it may cause LDH to grow excessively and become thick, affecting charge transport and bubble desorption.

[0069] In one embodiment of the present invention, the transition metal sulfide layer formed in step S2 is transformed into a nickel-iron oxide intercalation layer during a subsequent hydrothermal reaction.

[0070] In this embodiment, firstly, by defining the intermediate layer as being transformed into nickel-iron oxide under hydrothermal conditions (from step S3), it is clear that the intercalation is not a simple physical stacking, but rather a chemical reaction. This transformation process (such as the oxidation or hydrolysis of sulfides) allows the intermediate layer to form more stable chemical bonds (such as oxygen bridges) and a more continuous crystal structure at the interface with the substrate (foamed nickel-iron, which is essentially also a metal / oxide) and the upper catalyst layer (nickel-iron base layer of crystalline double hydroxide). This chemical fusion is far more robust than physical adhesion or simple heterojunction bonding, fundamentally solving the problem of easy catalyst layer detachment. This is the intrinsic chemical reason for achieving ultra-high structural stability of the electrode (such as long-term operation at a high current of 1.5 A / cm²).

[0071] Secondly, the decision to ultimately establish the intermediate layer as a nickel-iron oxide, rather than remaining in a sulfide state, has crucial functional significance. In the alkaline OER operating environment, oxides typically exhibit higher chemical stability and better conductivity compared to sulfides. This allows the intermediate layer to be adjusted into an interface layer that is stable and has superior conductivity in the electrolyte environment. Its lower resistance and better contact effectively improve the charge transport kinetics of the entire electrode, enabling the electrode to maintain its high catalytic activity (i.e., low overpotential) even at high current densities.

[0072] The method of the present invention will be further described below with reference to an exemplary embodiment.

[0073] like Figure 2 As shown, the method of the present invention may specifically include:

[0074] Step 1: Cut the foam NiFe substrate (Ni and Fe content ratio is 1:1) to a size of 5cm × 0.5cm.

[0075] Step 2: Place the cut NiFe foam substrate in a 1M HCl solution and sonicate for 30 minutes to remove the surface oxide layer. Afterwards, wash the substrate multiple times with water and ethanol, and then dry it.

[0076] Step 3: Prepare the precursor solution. Weigh 0.10812 g of nickel chloride hexahydrate, 0.095076 g of ferric chloride nonahydrate, and 0.12409 g of sodium thiosulfate pentahydrate using an analytical balance. Dissolve them in 100 ml of deionized water and stir at a constant speed until a light yellow, transparent, and clear solution is obtained.

[0077] Step 4: Place the washed foamed NiFe substrate in the precursor solution, let it stand for 15 hours, then remove it to obtain a black sample. Wash it multiple times with deionized water and ethanol, and then dry it.

[0078] Step 5: Prepare the NiFe-LDH precursor solution. Weigh 0.7361g of nickel nitrate hexahydrate, 0.3409g of ferric nitrate hexahydrate, 0.90075g of urea, and 0.222g of ammonium fluoride using an analytical balance. Dissolve them in 30ml of deionized water and stir at a constant speed until a clear, transparent, blue-green solution is obtained.

[0079] Step Six: After washing The film was transferred to a polytetrafluoroethylene reactor containing a NiFe-LDH precursor solution and reacted at 120°C for 4 hours.

[0080] Step 7: After the reaction vessel cools to room temperature, remove the sample, wash it multiple times with deionized water and ethanol, and dry it to obtain NiFe-LDH / / NFF target catalyst.

[0081] In this embodiment, it should be noted that, firstly, the method for testing the catalytic activity of the oxygen evolution reaction at the anode of water electrolysis is as follows: Electrochemical testing is performed using an electrochemical workstation (CHI760F) with a three-electrode system. The working electrode is the electrode of this invention, the counter electrode is a Pt wire, and the reference electrode is a mercury / mercury oxide electrode. The electrolyte is a 1M potassium hydroxide solution, and the test temperature is room temperature (25°C). The LSV test curve scan rate is 5 mV / s, and the voltage corresponds to the voltage of the reversible hydrogen electrode.

[0082] Second, the electrode is prepared by cutting the obtained electrode to a test active area of ​​0.3cm × 0.3cm. A 3cm length is left at the top of the electrode for connecting to the electrochemical workstation, and the remaining area is completely covered with hot melt adhesive.

[0083] Furthermore, the scanning electron microscopy characterization results are as follows: Figure 3 As shown, NiFe-LDH / / NFF material has a clear three-layer structure, consisting of NiFe-LDH from the outside in, and... And NFF. According to Figure 4 The SEM images show that the microstructure of the NiFe-LDH surface consists of nanospheres formed by interlacing nanosheets.

[0084] The electrochemical test results are as follows: Figure 5 As shown, for NiFe-LDH / / NFF material, at 100 At a current density of 100, the overpotential is 250 mV. For NiFe-LDH / NFF materials, at 100 At a current density of 100, the overpotential is 300 mV. For NFF materials, at 100 At a current density of [value missing], the overpotential is 303 mV. Therefore, compared to NiFe-LDH / NFF and NFF materials, NiFe-LDH / The / NFF material exhibited excellent catalytic activity in the OER catalytic reaction, which indicates that the introduction of the intermediate intercalation layer is beneficial to improving the OER catalytic reaction activity.

[0085] like Figure 6 As shown, the sample NiFe-LDH / in this invention The catalytic stability of the / NFF material was tested at 1.5... Under high current density, the material can be stably tested for 100 hours without significant activity decay.

[0086] In summary, the beneficial effects of the method of the present invention include at least the following:

[0087] First, the preparation method of this invention is simple and easy to scale up for industrial production.

[0088] Second, the preparation process of the present invention is through The introduction of an intermediate intercalation layer can significantly improve the bonding ability between the substrate and the catalyst layer, avoid the problem of catalyst layer detachment during the catalytic process, and improve stability.

[0089] Third, the introduction of intermediate intercalation can enhance the catalytic activity of the catalyst under high current density, thereby promoting the oxygen evolution reaction at a relatively small overpotential.

[0090] According to a second aspect of the present invention, a self-supporting anode catalyst is also provided, which is prepared by any of the technical solutions in the first aspect of the present invention. Its structure is a self-supporting three-layer composite structure, which consists of, from the outside to the inside: a nickel-iron substrate-like double hydroxide catalyst layer, a nickel-iron oxide intercalation layer, and a foamed nickel-iron substrate.

[0091] In this embodiment, the three-layer structure is not a simple stack, but a synergistic system. The outermost layer, a nickel-iron substrate-based double hydroxide catalyst layer, provides abundant electrochemical active sites for efficient oxygen evolution reaction (OER). The nickel-iron oxide intercalation layer serves as the intermediate layer, chemically anchoring the upper catalyst layer to the lower substrate to prevent detachment and improving interlayer electrical contact, thus reducing interfacial resistance. The foamed nickel-iron substrate acts as a support, providing a macroscopic three-dimensional conductive framework and mechanical strength. This gradient functional design of "active layer-interfacial reinforcement layer-conductive framework" enables the catalyst product to achieve a structural unity of high activity, strong binding, and rapid conduction.

[0092] In one embodiment of the present invention, the nickel-iron-based double hydroxide catalyst layer of the present invention has a nanosphere micromorphology formed by interlacing nanosheets.

[0093] Thus, the catalyst layer, with its "nanosphere-like microstructure formed by interwoven nanosheets," is not a dense, smooth thin film, but rather an open structure with an extremely high specific surface area and abundant three-dimensional pores. The nanosheets themselves provide a large number of surface atoms as potential catalytic active sites, and these nanosheets further interweave and assemble into nanospheres, avoiding the tight stacking of the sheets and constructing an interconnected, open network of pores at the micron and nanoscale. This greatly promotes the diffusion and transport of electrolyte ions to the active sites within the catalyst, while also facilitating the rapid desorption of oxygen bubbles generated during the reaction, preventing bubble blockage of the active sites.

[0094] According to a third aspect of the present invention, the application of a self-supporting anode catalyst according to any of the technical solutions in the second aspect of the present invention in the oxygen evolution reaction of water electrolysis is also provided.

[0095] Because the self-supporting anode catalyst of this invention is itself a "self-supporting" structure (integrating the active material, conductive layer, and substrate into one), it eliminates the complex steps required by traditional powder catalysts, such as mixing with binders and coating onto the current collector, which may introduce interfacial resistance or instability. Therefore, this application greatly simplifies electrode preparation and application, ensuring that the structural advantages of the product (such as strong interlayer bonding) are not compromised or weakened in the final use stage. This allows its excellent bulk properties (such as high stability) to be directly and completely transformed into high performance and long lifespan in actual electrolysis devices.

[0096] In one embodiment of the present invention, the self-supporting anode catalyst is specifically applied to the anodic oxygen evolution reaction in an alkaline or anion exchange membrane water electrolysis system.

[0097] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a self-supporting anode catalyst, characterized in that, Includes the following steps: Step S1: Provide and pre-treat the foamed nickel-iron substrate; Step S2: Immerse the pretreated foamed nickel-iron substrate in the first precursor solution and allow it to react statically. A transition metal sulfide layer is formed in situ on the substrate surface. After washing and drying, the intermediate product is obtained. Step S3: The intermediate product is placed in the second precursor solution for hydrothermal reaction to grow a layered double hydroxide catalyst layer on the surface of the transition metal sulfide layer, thereby obtaining a self-supporting anode catalyst with a three-layer structure of layered double hydroxide, transition metal oxide, and foamed nickel iron. The first precursor solution contains nickel salt, iron salt and sulfur source; the second precursor solution contains nickel salt, iron salt, urea and ammonium fluoride.

2. The method for preparing the self-supporting anode catalyst according to claim 1, characterized in that, In step S1, the ratio of nickel to iron in the foamed nickel-iron substrate is 1:1; the pretreatment specifically includes: placing the foamed nickel-iron substrate in an acid solution for ultrasonic cleaning to remove the surface oxide layer, and then washing it with water and ethanol in sequence and drying it.

3. The method for preparing the self-supporting anode catalyst according to claim 2, characterized in that, The acid solution is a 1 mol / L hydrochloric acid solution, and the ultrasonic cleaning time is 25 to 35 minutes.

4. The method for preparing the self-supporting anode catalyst according to claim 1, characterized in that, In step S2, the nickel salt in the first precursor solution is nickel chloride hexahydrate, the iron salt is ferric chloride nonahydrate, and the sulfur source is sodium thiosulfate pentahydrate; the static reaction is carried out at room temperature and pressure for 14 to 16 hours.

5. The method for preparing the self-supporting anode catalyst according to claim 1, characterized in that, In step S3, the nickel salt in the second precursor solution is nickel nitrate hexahydrate, and the iron salt is ferric nitrate hexahydrate; the hydrothermal reaction is carried out at a temperature of 100°C to 120°C for 4 hours.

6. The method for preparing the self-supporting anode catalyst according to any one of claims 1-5, characterized in that, The transition metal sulfide layer formed in step S2 is transformed into a nickel-iron oxide intercalation layer during the subsequent hydrothermal reaction.

7. A self-supporting anode catalyst, characterized in that, The preparation method described in any one of claims 1-6 is used to obtain the structure of a self-supporting three-layer composite structure, which consists of, from the outside to the inside: a nickel-iron substrate-like double hydroxide catalyst layer, a nickel-iron oxide intercalation layer, and a foamed nickel-iron substrate.

8. The self-supporting anode catalyst according to claim 7, characterized in that, The nickel-iron base layer of double hydroxide catalyst has a nanosphere microstructure formed by interlaced nanosheets.

9. The application of a self-supporting anode catalyst as described in claim 7 or 8 in the oxygen evolution reaction of water electrolysis.

10. The application according to claim 9, characterized in that, Specifically applied to the anodic oxygen evolution reaction in alkaline or anion exchange membrane water electrolysis systems.

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