Self-supporting Fe-Ni3S2-coated NiCoLDH core-shell electrocatalyst, preparation method thereof and hydrogen production method

Abstract

The invention provides a self-supporting Fe-Ni3S2-coated NiCoLDH core-shell electrocatalyst, a preparation method thereof and a hydrogen production method, and relates to the field of catalysts. The self-supporting Fe-Ni3S2-coated NiCoLDH core-shell electrocatalyst comprises a conductive nickel substrate and a core-shell electrocatalyst arranged on the surface of the conductive nickel substrate, a core in the core-shell electrocatalyst comprises iron-doped nickel sulfide nanosheets, and a shell comprises nickel-cobalt layered double hydroxides. The core and the shell are tightly connected through strong chemical bonding, so that the material keeps structural integrity under a harsh electro-catalysis working condition, and active components are effectively prevented from falling off; the iron-doped nickel sulfide nanosheet with excellent conductivity is used as a natural framework, an efficient electron transmission path is provided for an external nickel-cobalt layered double-metal hydroxide shell layer, the internal resistance of the electrode is remarkably reduced, and reaction kinetics is accelerated.

Description

Technical Field

[0001] This application relates to the field of catalysts, and more particularly to a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, its preparation method, and a method for hydrogen production. Background Technology

[0002] Electrocatalytic water splitting for hydrogen production, especially at high current densities, is considered a key approach to addressing the increasingly severe energy crisis and environmental pollution problems. However, the slow kinetics and high overpotential of the oxygen evolution reaction (OER) are the main bottlenecks limiting overall water splitting efficiency. In recent years, two-dimensional transition metal layered double hydroxides (LDHs) have attracted widespread attention in the electrocatalysis of the alkaline oxygen evolution reaction (OER) due to their low cost, abundant reserves, and high intrinsic activity, and are considered one of the most promising catalytic materials to replace precious metals.

[0003] However, the inherent low conductivity and easy aggregation of these materials hinder further improvement in their electrocatalytic performance. To overcome these limitations, various modification strategies have emerged, such as the preparation of ultrathin LDH nanosheets, defect engineering, and interface engineering. Although some materials exhibit excellent oxygen evolution performance after surface modification, most layered double hydroxides still suffer from poor electronic conductivity and limited active sites, which directly leads to difficulties in meeting industrialization requirements in terms of active site utilization and material stability.

[0004] Therefore, it is urgent to explore a non-precious metal catalyst with high activity and stability. Summary of the Invention

[0005] The purpose of this application is to provide a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, its preparation method, and a method for hydrogen production, so as to solve the problems of unsatisfactory OER catalytic activity and stability of LDH catalysts under alkaline conditions.

[0006] To achieve the above objectives, the first aspect of this application provides a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, comprising a conductive nickel substrate and a core-shell electrocatalyst disposed on the surface of the conductive nickel substrate; The core of the core-shell electrocatalyst comprises iron-doped nickel sulfide nanosheets, and the shell comprises nickel-cobalt layered bimetallic hydroxide.

[0007] Optionally, the mass ratio of iron, sulfur, cobalt and nickel in the core-shell electrocatalyst is 5-10:10-20:15-25:30-40; And / or, the thickness of the core is 50-60 nm; And / or, the thickness of the shell is 160-170 nm; And / or, the thickness of the core-shell electrocatalyst is 230-240 nm.

[0008] A second aspect of this application provides a method for preparing the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, comprising: The conductive substrate is pretreated to obtain the pretreated conductive substrate; The pretreated conductive matrix, iron source, and sulfur source are mixed and subjected to a hydrothermal reaction to obtain an iron-modified nickel sulfide nanosheet precursor. The iron-modified nickel sulfide nanosheet precursor, nickel source, cobalt source and water were first mixed and electrodeposited to obtain a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst.

[0009] Optionally, the pretreatment includes: sequentially subjecting the conductive substrate to solvent ultrasonication, a first water wash, an acid wash, and a second water wash.

[0010] Optionally, the solvent in the solvent ultrasound includes one or more of acetone, ethanol, and isopropanol; And / or, the acid in the pickling includes one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and oxalic acid; The concentration of the acid is 1-6 M; And / or, the solvent is sonicated for 5-30 minutes; And / or, the pickling time is 5-30 min.

[0011] Optionally, the conductive substrate includes one or more of nickel mesh, nickel felt, nickel foam, stainless steel mesh, and carbon paper; And / or, the iron source includes one or more of ferric nitrate, ferric chloride, and ferrous sulfate; And / or, the sulfur source includes one or more of sodium sulfide, thiourea, and thioacetamide; And / or, the nickel source includes one or more of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel aminosulfonate, and nickel fluoroborate; And / or, the cobalt source includes one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt sulfamate, and cobalt fluoroborate.

[0012] Optionally, the molar ratio of the iron source to the sulfur source is 0.6-1.2:2-5; And / or, the molar ratio of the nickel source to the cobalt source is 1-3:1-3.

[0013] Optionally, the hydrothermal reaction is carried out at a temperature of 120-180℃ for 4-8 hours.

[0014] Optionally, the electrodeposition voltage is -0.8V to -1.2V, the temperature is room temperature, and the time is 50-800s.

[0015] A third aspect of this application provides a method for producing hydrogen, comprising using the aforementioned self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst as an anode for water electrolysis to produce hydrogen.

[0016] Compared with the prior art, the beneficial effects of this application include: The self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst provided in this application possesses a clearly defined layered core-shell heterostructure, with performance advantages manifested in multiple aspects: the core and shell are tightly connected through strong chemical bonds, maintaining structural integrity under harsh electrocatalytic conditions and effectively preventing the shedding of active components; the iron-doped nickel sulfide nanosheets (Fe-Ni3S2) with excellent conductivity serve as a natural framework, providing an efficient electron transport path for the outer nickel-cobalt layered bimetallic hydroxide (NiCoLDH) shell, significantly reducing the internal resistance of the electrode and accelerating reaction kinetics; strong electronic interactions occur between the core and shell at the interface, significantly enhancing the intrinsic catalytic activity of the material by synergistically regulating the adsorption free energy of reaction intermediates, achieving a synergistic enhancement effect beyond that of a single component. Furthermore, in this layered core-shell structure, the NiCoLDH shell inherits the three-dimensional porous framework of the Fe-Ni3S2 substrate, which not only facilitates the full penetration of electrolytes but also promotes the rapid release of oxygen during the reaction, thereby significantly improving the mass transfer efficiency and reaction activity of the catalyst. These characteristics make this catalyst a promising candidate for application in energy conversion fields such as industrial water electrolysis for hydrogen production.

[0017] This application provides a method for preparing a self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst. This method involves a two-step process to controllably construct a layered core-shell heterostructure: First, large-sized iron-doped nickel sulfide nanosheets are grown in situ on a conductive substrate using a hydrothermal method. The conductive substrate serves as both a support and a nickel source, achieving strong bonding and excellent electrical contact. The incorporation of iron ions not only modulates the microstructure of the nanosheets but also optimizes their electronic properties. Subsequently, a constant-potential electrodeposition technique is used. Under negative bias, a water reduction reaction occurs at the cathode, leading to an increase in the interfacial pH and promoting the oxidation of Ni. 2+ and Co 2+ Ions and the generated OH -This process combines nickel and cobalt to form a small-sized nickel-cobalt layered bimetallic hydroxide layer on iron-doped nickel sulfide nanosheets. This process allows the precursor to maintain its nanosheet structure while increasing surface roughness, thereby increasing specific surface area, shortening ion / electron transport paths, and enhancing conductivity. Furthermore, the introduction of nickel and cobalt further improves the electronic structure of Fe-Ni3S2, significantly enhancing the catalyst's electrochemical performance and long-term stability, supporting its potential in industrial electrocatalytic applications. This preparation process, combining hydrothermal reaction with electrodeposition technology, significantly simplifies the operation, reduces process variables, improves batch consistency, and facilitates large-scale manufacturing.

[0018] The hydrogen production method provided in this application, with a self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst as the anode, shows potential for application in the field of industrial water electrolysis for hydrogen production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 SEM image of Fe-Ni3S2@NiCoLDH-300 provided in Example 1; Figure 2 SEM image of the Ni3S2 electrocatalyst provided in Comparative Example 1; Figure 3 SEM image of the NiCoLDH electrocatalyst provided in Comparative Example 2; Figure 4 SEM image of the Fe-Ni3S2 electrocatalyst provided in Comparative Example 3; Figure 5 Linear sweep voltammetry results of the electrocatalysts provided in Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 in 1M KOH electrolyte; Figure 6 The Tafel slope test results of the electrocatalysts provided in Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 in 1M KOH electrolyte are shown in the figure. Figure 7 EIS test results of the electrocatalysts provided in Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 in 1M KOH electrolyte; Figure 8The electrocatalysts provided in Examples 1, 2, 3, Comparative Examples 1, 2, 3, and 4 in 1M KOH electrolyte, C dl Test result graph; Figure 9 Comparative graph showing the stability evaluation of the electrocatalysts provided in Example 1 and Comparative Example 2 in 1M KOH electrolyte; Figure 10 The graph shows a comparison of the total hydrolysis performance of the dual-electrode systems consisting of Example 1 and Comparative Example 4 as anodes and Comparative Example 5 as cathodes in 1M KOH electrolyte. Figure 11 The graph shows a comparison of the stability of the dual-electrode system consisting of Example 1 as the anode and Comparative Example 5 as the cathode in 1 M KOH electrolyte. Figure 12 Linear sweep voltammetry comparison graphs of the electrocatalysts provided in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 in 6M KOH electrolyte; Figure 13 The stability evaluation diagram of the electrocatalyst provided in Example 1 in 6M KOH electrolyte; Figure 14 The graph shows the performance evaluation of the two-electrode system consisting of Example 1 and Comparative Example 4 as anodes and Comparative Example 5 as cathode in 6M KOH electrolyte. Figure 15 The graph shows the stability evaluation of the two-electrode system consisting of Example 1 as the anode and Comparative Example 5 as the cathode in 6M KOH electrolyte for the complete water decomposition. Figure 16 a is a transmission electron microscope (TEM) image of Example 1, b is a high-resolution transmission electron microscope (HRTEM) image, c is a selected electron diffraction (SAED) image, and d is an energy-dispersive X-ray (EDS) image. Figure 17 X-ray diffraction (XRD) patterns of the electrocatalysts provided in Example 1, Comparative Example 1, and Comparative Example 3; Figure 18 Raman diagrams of the electrocatalysts provided in Example 1 and Comparative Examples 1, 2 and 3. Detailed Implementation

[0021] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, comprising a conductive nickel substrate and a core-shell electrocatalyst disposed on the surface of the conductive nickel substrate; The core of the core-shell electrocatalyst comprises iron-doped nickel sulfide nanosheets, and the shell comprises nickel-cobalt layered bimetallic hydroxide.

[0022] It is worth noting that the highly conductive iron-doped nickel sulfide nanosheets (Fe-Ni3S2 nanosheets) ensure rapid charge transfer, while the amorphous nickel-cobalt layered bimetallic hydroxide (NiCoLDH) nanosheets with abundant defects provide many exposed active sites. At the same time, the unique 3D layered core-shell nanostructure of this self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst creates favorable conditions for electrolyte diffusion and the release of gaseous products. Based on the above characteristics, this Fe-Ni3S2@NiCo-LDH catalyst can be directly used as a working electrode, exhibiting high activity, excellent stability, and good durability in the oxygen evolution reaction.

[0023] In some embodiments, the mass ratio of iron, sulfur, cobalt and nickel in the core-shell electrocatalyst is 5-10:10-20:15-25:30-40; Optionally, the mass ratio of iron, sulfur, cobalt and nickel in the core-shell electrocatalyst can be (5:10:15:30), (10:10:15:30), (5:15:15:30), (5:20:15:30), (5:10:20:30), (5:10:25:30), (5:10:15:35), (5:10:15:40), (10:20:25:40) or any value between 5-10:10-20:15-25:30-40; And / or, the thickness of the core is 50-60 nm; Optionally, the thickness of the core can be 50nm, 55nm, or 60nm, and can be any value between 50-60nm; And / or, the thickness of the shell is 160-170 nm; Optionally, the thickness of the shell can be 160nm, 165nm, 170nm or any value between 160-170nm; And / or, the thickness of the core-shell electrocatalyst is 230-240 nm.

[0024] Optionally, the thickness of the core-shell electrocatalyst can be any value between 230 nm, 235 nm, 240 nm, or 230-240 nm.

[0025] A second aspect of this application provides a method for preparing the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, comprising: The conductive substrate is pretreated to obtain the pretreated conductive substrate; The pretreated conductive matrix, iron source, and sulfur source are mixed and subjected to a hydrothermal reaction to obtain an iron-modified nickel sulfide nanosheet precursor. The iron-modified nickel sulfide nanosheet precursor, nickel source, cobalt source and water were first mixed and electrodeposited to obtain a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst.

[0026] It is worth noting that the preparation sequence of first hydrothermal synthesis and then electrodeposition can effectively maintain the initial morphology of Fe-Ni3S2 nanosheets and promote the uniform growth of nickel-cobalt layered double hydroxides on the nanosheet surface, thereby forming a regular core-shell structure (such as Fe-Ni3S2@NiCo-LDH). This strategy not only avoids the problem of active material agglomeration caused by uneven substrate surface energy in traditional electrodeposition, but also improves the consistency and reproducibility of the material, which is beneficial for large-scale production.

[0027] In some embodiments, the pretreatment includes: sequentially subjecting the conductive substrate to solvent ultrasonication, a first water wash, an acid wash, and a second water wash.

[0028] In some embodiments, the conductive substrate is selected from nickel mesh, nickel felt, nickel foam and carbon paper, preferably nickel foam with a size of 1.5mm×200mm×300mm and a pore size of 0.1mm; In some embodiments, the solvent in the solvent ultrasound includes one or more of acetone, ethanol, and isopropanol; And / or, the acid in the pickling includes one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and oxalic acid; Preferably, the acid used in pickling includes hydrochloric acid; The concentration of the acid is 1-6M; Optionally, the concentration of the acid can be 1M, 2M, 3M, 4M, 5M, 6M or any value between 1 and 6M; Preferably, the acid concentration is 1-3M; And / or, the solvent is sonicated for 5-30 minutes; Optionally, the time for solvent sonication can be any value between 5 min, 10 min, 20 min, 30 min, or 5-30 min; And / or, the pickling time is 5-30 min.

[0029] Optionally, the pickling time can be any value between 5 min, 10 min, 20 min, 30 min, or 5-30 min.

[0030] In some embodiments, the conductive substrate includes one or more of nickel mesh, nickel felt, nickel foam, stainless steel mesh, and carbon paper; And / or, the iron source includes one or more of ferric nitrate, ferric chloride, and ferrous sulfate; And / or, the sulfur source includes one or more of sodium sulfide, thiourea, and thioacetamide; And / or, the nickel source includes one or more of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel aminosulfonate, and nickel fluoroborate; And / or, the cobalt source includes one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt sulfamate, and cobalt fluoroborate.

[0031] In some embodiments, the molar ratio of the iron source to the sulfur source is 0.6-1.2:2-5; Optionally, the molar ratio of iron source to sulfur source can be any value between 0.6:2, 0.9:2, 1.2:2, 0.9:3, 0.9:4, 0.9:5, or 0.6-1.2:2-5; In some embodiments, the amount of iron source is 0.6-1.2 mmol, preferably 0.6 mmol; In some embodiments, the amount of sulfur source is 2-5 mmol / L, preferably 3.0 mmol / L; And / or, the molar ratio of the nickel source to the cobalt source is 1-3:1-3.

[0032] Optionally, the molar ratio of the nickel source to the cobalt source can be any value between 1:1, 1:2, 1:3, 2:1, 3:1, or 1-3:1-3; In some embodiments, the concentration of the nickel source is 10-30 mmol / L, preferably 15 mmol / L; In some embodiments, the concentration of the cobalt source is 15 mmol / L; In some embodiments, the hydrothermal reaction is carried out at a temperature of 120-180°C for a duration of 4-8 hours.

[0033] Optionally, the temperature of the hydrothermal reaction can be any value between 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃ or 120-180℃, and the time can be any value between 4h, 5h, 6h, 7h, 8h or 4-8h.

[0034] In some embodiments, the electrodeposition voltage is -0.8V to -1.2V, the temperature is room temperature, and the time is 50-800s.

[0035] Optionally, the electrodeposition voltage can be any value between -0.8V, -0.9V, -1V, -1.1V, -1.2V, or -0.8V--1.2V, and the time can be any value between 50s, 100s, 200s, 300s, 400s, 500s, 600s, 700s, 800s, or 50-800s.

[0036] Preferably, the electrodeposition voltage is -0.9V to -1.2V, and the time is 100-500s.

[0037] In some embodiments, electrodeposition employs a three-electrode system, including a working electrode, a counter electrode, and a reference electrode. The working electrode is an iron-modified nickel sulfide nanosheet precursor obtained by hydrothermal treatment, Ag / AgCl is used as the reference electrode, and a platinum sheet is used as the counter electrode.

[0038] A third aspect of this application provides a method for producing hydrogen, comprising using the aforementioned self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst as an anode for water electrolysis to produce hydrogen.

[0039] In some embodiments, a self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst is used as the anode, and a cathode counter electrode and a reference electrode are provided, with a concentration of 1-6 mol L⁻¹. -1 KOH aqueous solution was used as the electrolyte to carry out the water electrolysis reaction at room temperature. Preferably, 1 and 6 mol / L... -1 KOH aqueous solution was used as the electrolyte.

[0040] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0041] Example 1 The first aspect of this embodiment provides a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, comprising a conductive nickel substrate and a core-shell electrocatalyst disposed on the surface of the conductive nickel substrate; The core of the core-shell electrocatalyst consists of iron-doped nickel sulfide nanosheets, and the shell consists of nickel-cobalt layered bimetallic hydroxide.

[0042] SEM images of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst are shown below. Figure 1As shown, the left image is a low-magnification SEM image, and the right image is a high-magnification SEM image. It can be seen from the images that a layer of small NiCoLDH nanosheets is uniformly covered on the surface of Fe-Ni3S2, forming a hierarchical core-shell heterostructure. In the Fe-Ni3S2@NiCoLDH hierarchical nanosheet structure, the NiCoLDH nanosheets inherit the three-dimensional porous framework of the Fe-Ni3S2 substrate, which is conducive to the permeation of electrolytes and the release of oxygen.

[0043] The second aspect of this embodiment provides a method for preparing a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, comprising: Preparation of S1 and Fe-Ni3S2 precursors: 0.2424 g Fe(NO3)3·9H2O and 0.7220 g Na2S·9H2O were dissolved in 15 mL of deionized water respectively. After complete dissolution, the two solutions were mixed and stirred to form a black homogeneous solution. The black homogeneous solution was transferred to the lining of an 80 mL reactor and the pretreated nickel foam was transferred to the reactor. The reactor was hydrothermally reacted at 150 °C for 6 hours. After cooling to room temperature, the sample was taken out, washed with water and alcohol three times, and then dried in a vacuum drying oven at 60 °C for 6 hours to obtain the iron-modified nickel sulfide nanocatalyst precursor (Fe-Ni3S2 precursor) grown on the conductive nickel foam substrate. It is denoted as Fe-Ni3S2. The pretreatment method for nickel foam is as follows: cut the nickel foam into 4-8 square centimeters, first sonicate it in acetone solution for 10-20 minutes to remove surface organic matter, then "replace" the residual acetone in the pores of the nickel foam with anhydrous ethanol, and then sonicate it in deionized water solution, dilute acid solution and deionized water solution for 10-20 minutes each to obtain pretreated clean nickel foam. Preparation of S2 and Fe-Ni3S2@NiCoLDH core-shell electrocatalyst: 0.75 mmol Ni(NO3)3·6H2O and 0.75 mmol Co(NO3)3·6H2O were dissolved in 50 mL of deionized water and stirred evenly to form the electrolyte. The Fe-Ni3S2 precursor obtained in step S1 was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system. Using a constant voltage method, an external voltage of -1V was applied at room temperature, and NiCoLDH was grown on the surface of Fe-Ni3S2 for 300 s. Subsequently, the catalyst was washed three times with water and ethanol and dried in a vacuum drying oven at 60 °C for 6 hours to obtain the Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, denoted as Fe-Ni3S2@NiCoLDH-300s.

[0044] Example 2 Unlike Example 1, the product was prepared by electrodeposition in the electrolyte above, with a deposition time of 100s. The final product was Fe-Ni3S2@NiCoLDH, denoted as Fe-Ni3S2@NiCoLDH-100s.

[0045] Example 3 Unlike Example 1, the product was prepared by electrodeposition in the above electrolyte for 500 s, and the final product was Fe-Ni3S2@NiCoLDH, denoted as Fe-Ni3S2@NiCoLDH-500s.

[0046] Comparative Example 1 Compared with Example 1, the difference is that no iron source was added before the hydrothermal reaction, and 0.7220g of Na2S·9H2O was directly dissolved in 30mL of deionized water. The final product is Ni3S2 electrocatalyst, denoted as Ni3S2.

[0047] SEM images of the Ni3S2 electrocatalyst are shown below. Figure 2 As shown in the figure, the left image is a low-magnification SEM image and the right image is a high-magnification SEM image. The figures show that Ni3S2 was successfully grown on nickel foam and also shows a nanoridge structure.

[0048] Comparative Example 2 Compared with Example 1, the difference is that no Fe-Ni3S2 precursor was prepared, and NiCoLDH was directly deposited on NF. The electrolyte was prepared by dissolving 0.75 mmol Ni(NO3)3·6H2O and 0.75 mmol Co(NO3)3·6H2O in 50 mL of deionized water. The final product is NiCoLDH electrocatalyst, denoted as NiCoLDH.

[0049] SEM images of the NiCoLDH electrocatalyst are shown below. Figure 3 As shown in the figure, the left image is a low-magnification SEM image and the right image is a high-magnification SEM image. It can be seen from the figure that NiCoLDH is a cross-linked nanosheet structure. Compared with NiCoLDH deposited on Fe-Ni3S2 precursor, the latter inherits the three-dimensional porous framework of Fe-Ni3S2 precursor, which is conducive to electrolyte permeation and oxygen release.

[0050] Comparative Example 3 Compared with Example 1, the difference is that only the Fe-Ni3S2 precursor was prepared, without electrodeposition, and the final product was the Fe-Ni3S2 electrocatalyst, denoted as Fe-Ni3S2.

[0051] SEM images of the Fe-Ni3S2 electrocatalyst are shown below. Figure 4As shown, the left image is a low-magnification SEM image, and the right image is a high-magnification SEM image. It can be seen that Fe-Ni3S2 has a nanosheet structure, which is significantly different from the structure of Ni3S2, indicating that Fe³⁺… + The introduction of [a specific substance] can regulate the morphology of Ni3S2.

[0052] Comparative Example 4 The conventional electrocatalyst was prepared as follows: 5 mg RuO2 powder was mixed with 1 mL ethanol solution and 80 μL Nafion solution was added. After sonication for 30 min, 500 μL of the mixture was dropped onto pretreated NF (1 x 4 cm) and dried to obtain the RuO2 electrocatalyst, denoted as RuO2.

[0053] Comparative Example 5 The conventional electrocatalyst was prepared as follows: 5 mg of Pt / C powder was mixed with 1 mL of ethanol solution and 80 μL of Nafion solution was added. After sonication for 30 min, 500 μL of the mixture was dropped onto pretreated NF (1 × 4 cm) and dried to obtain the Pt / C electrocatalyst, denoted as Pt / C.

[0054] Comparative Example 6 Compared with Example 1, the difference is that Na2S·9H2O is not added in step S1, and the final product is NiFe@NiCoLDH catalyst, denoted as NiFe@NiCoLDH.

[0055] Comparative Example 7 Compared with Example 1, the difference is that in step S2, 0.75 mmol Co(NO3)3·6H2O is not added, and the final product is Fe-Ni3S2@NiLDH catalyst, denoted as Fe-Ni3S2@NiLDH.

[0056] Comparative Example 8 Compared with Example 1, the difference is that in step S2, 0.75 mmol Ni(NO3)3·6H2O is not added, and the final product is Fe-Ni3S2@CoLDH catalyst, denoted as Fe-Ni3S2@CoLDH.

[0057] The electrocatalysts provided in the above examples and comparative examples were subjected to electrochemical performance testing. Specifically, the electrocatalysts provided in the above examples and comparative examples were used as working electrodes, Hg / HgO as reference electrodes, and graphite rods as counter electrodes. The electrolyte was 1 mol L⁻¹. -1 KOH solution, scan rate 5 mV s -1 Linear sweep voltammetry (LSV), Tafel slope, and double-layer capacitance (C0) were performed on the Chenhua electrochemical workstation (CHI660E).dl The results of the tests, including electrochemical impedance spectroscopy (EIS), are shown in Table 1.

[0058] Table 1 Electrochemical Performance Tests

[0059] The linear sweep voltammetry (LSV) results for Examples 1 (Fe-Ni3S2@NiCoLDH-300s), 2 (Fe-Ni3S2@NiCoLDH-100s), 3 (Fe-Ni3S2@NiCoLDH-500s), Comparative Example 1 (Ni3S2), Comparative Example 2 (NiCoLDH), Comparative Example 3 (Fe-Ni3S2), and Comparative Example 4 (RuO2) are as follows: Figure 5 As shown, the Tafel slope results are as follows: Figure 6 As shown, the EIS results are as follows: Figure 7 As shown, C dl The result is as follows Figure 8 As shown. Figure 5 The LSV curves show that through Fe modification and the synergistic effect of nickel and cobalt in Fe-Ni3S2 and NiCoLDH, the sample exhibits improved performance at 100 mA cm⁻¹. -2 The overpotential at the time of deposition was significantly better than that of Examples 2, 3, 1, 2, 3, and 4. Furthermore, a comparison with Examples 1, 2, and 3 showed that increasing the NiCoLDH deposition time improved the catalyst performance; however, the catalytic activity began to decline after electrodeposition time exceeded 300 s. This result can be attributed to the controllable nucleation and growth behavior of NiCo LDH nanosheets on the Fe-Ni3S2 surface during electrodeposition. Under the optimized 300 s deposition conditions, NiCo LDH nanosheets formed a uniform and appropriately dense capping layer on the Fe-Ni3S2 substrate, providing a sufficient active interface while avoiding blockage of active sites due to excessive accumulation. However, further extension of the deposition time led to significant overgrowth of NiCo LDH, resulting in the covering of active sites on the Fe-Ni3S2 nanosheets, hindering the mass transfer pathways of reactants and intermediates, and ultimately reducing catalytic performance. Figure 6 The Tafel slope plot shows that Fe-Ni3S2@NiCoLDH has a low Tafel slope (38.2 mV dec). -1 This indicates that the reaction kinetics are relatively fast. This result was also... Figure 7 As confirmed by the EIS results shown, Fe-Ni3S2@NiCoLDH (0.43Ω) exhibits the smallest semicircular and charge transfer resistance. Figure 8 C dlThe figure shows that the Fe-Ni3S2@NiCoLDH catalyst has a large ECSA, which leads to improved catalytic performance. These results indicate that the Fe-doped Ni3S2 nanosheet array not only has a larger surface area and more exposed active sites than Ni3S2, but also has better conductivity than pure Ni3S2. This not only facilitates the uniform growth of nickel-cobalt layered double hydroxides on the nanosheet surface, avoiding the agglomeration problem of active materials caused by uneven substrate surface energy in traditional electrodeposition, but also ensures the effective charge transfer of the 3D core-shell structure catalyst.

[0060] Stability experiments were conducted on Example 1 (Fe-Ni3S2@NiCoLDH-300s) and Comparative Example 2 (NiCoLDH) in a single-cell electrolytic cell. The test results are as follows: Figure 9 As shown, specifically: the Fe-Ni3S2@NiCoLDH catalyst and NiCoLDH catalyst provided in Example 1 (Fe-Ni3S2@NiCoLDH-300s) and Comparative Example 2 (NiCoLDH) were used as anodes, and 1 mol L... -1 KOH aqueous solution was used as the electrolyte, and the current density was 500 mA / cm² at room temperature. -2 The electrochemical oxygen evolution reaction was carried out. The Fe-Ni3S2@NiCoLDH-300s catalyst provided in Example 1 maintained stable cell pressure and showed no significant degradation after approximately 260 hours; the NiCoLDH catalyst provided in Comparative Example 2 showed a gradual increase in cell pressure and a significant performance degradation after approximately 80 hours. The comparison shows that the Fe-Ni3S2@NiCoLDH-300s catalyst prepared in Example 1 exhibits excellent stability, mainly due to the strong mechanical stability of the Fe-Ni3S2 substrate and the strong electronic interactions between the core and shell in the core-shell structure, effectively suppressing structural degradation caused by dissolution and bubble erosion.

[0061] The Fe-Ni3S2@NiCoLDH-300s catalyst obtained in Example 1 and the RuO2 catalyst obtained in Comparative Example 4 were used as anodes, and the Pt / C catalyst obtained in Comparative Example 5 was used as cathode, forming a two-electrode system. 1 mol L -1 KOH aqueous solution was used as the electrolyte, and the current density was 500 mA cm⁻¹ at room temperature. -2 The following tests were conducted to assess the overall water splitting performance. The specific test results are as follows: Figure 10 As shown. The Fe-Ni3S2@NiCoLDH-300s catalyst obtained in Example 1 was used as the anode, and the Pt / C catalyst obtained in Comparative Example 5 was used as the cathode. The results of the stability test of the two-electrode system for total water splitting are shown below. Figure 11As shown, the Fe-Ni3S2@NiCoLDH-300s catalyst maintained stable cell pressure and showed no significant degradation after approximately 240 hours.

[0062] Example 1 (Fe-Ni3S2@NiCoLDH-300s), Comparative Example 1 (Ni3S2), Comparative Example 2 (NiCoLDH), Comparative Example 3 (Fe-Ni3S2), and Comparative Example 4 (RuO2) were used as working electrodes, Hg / HgO as reference electrodes, and graphite rods as counter electrodes. The electrolyte was 6 mol / L. -1 KOH solution, scan rate 5 mV s -1 Linear scan voltammetry was performed using the Chenhua electrochemical workstation (CHI660E); the results are shown in the figure below. Figure 12 As shown.

[0063] The Fe-Ni3S2@NiCoLDH-300s catalyst provided in Example 1 was subjected to a stability experiment in a single-cell electrolyzer, and the results are as follows: Figure 13 As shown, specifically: Fe-Ni3S2@NiCoLDH-300s catalyst electrode is used as the anode, 6 mol L... -1 KOH aqueous solution was used as the electrolyte, and the current density was 500 mA cm⁻¹ at room temperature. -2 Electrochemical oxygen evolution reaction was carried out. After about 120 hours, the Fe-Ni3S2@NiCoLDH-300s catalyst maintained stable cell pressure without significant degradation, indicating that it has good stability even under extreme conditions.

[0064] The Fe-Ni3S2@NiCoLDH-300s catalyst obtained in Example 1 and the RuO2 catalyst obtained in Comparative Example 4 were used as anodes, and the Pt / C catalyst obtained in Comparative Example 5 was used as cathode, forming a two-electrode system. 6 mol L -1 Using KOH aqueous solution as the electrolyte, the total water decomposition performance was tested at room temperature. The results are shown in the figure below. Figure 14 As shown.

[0065] The Fe-Ni3S2@NiCoLDH-300s catalyst obtained in Example 1 was used as the anode, and the Pt / C catalyst obtained in Comparative Example 5 was used as the cathode, forming a two-electrode system. (6 mol L) -1 Using KOH aqueous solution as the electrolyte, at room temperature and a current density of 500 mA cm⁻¹ -2 The stability test of the full water splitting catalyst was conducted. The results showed that the Fe-Ni3S2@NiCoLDH-300s catalyst maintained stable cell pressure and showed no significant degradation after about 100 hours. The results are shown in the figure below. Figure 15 As shown.

[0066] Figure 16 To further investigate the microstructure of Example 1 (Fe-Ni3S2@NiCoLDH-300s), TEM tests were performed, and the results are shown in Figure 16.

[0067] TEM observation ( Figure 16 a) This confirmed that Example 1 (Fe-Ni3S2@NiCoLDH-300s) was a nanosheet assembly, consistent with the SEM results. High-resolution TEM (HRTEM) imaging ( Figure 16 b) shows distinct lattice fringes with spacings of 0.28 nm and 0.18 nm, corresponding to the (110) and (113) crystal planes of Ni3S2, respectively. Selected area electron diffraction (SAED) pattern ( Figure 16 c) exhibits polycrystalline properties, with diffraction points pointing to the (003) plane of NiCo LDH and the (101) and (110) planes of Ni3S2. Furthermore, energy-dispersive X-ray spectroscopy (EDS) elemental mapping ( Figure 16 d) Confirmed the successful bonding of iron and the formation of a layered core-shell structure. Specifically, the signals of Fe and S were mainly concentrated in the inner layer, while the signals of Co and O were uniformly distributed in the outer layer, which provides strong evidence for the layered core-shell heterostructure of Fe-Ni3S2@NiCoLDH-300s.

[0068] The XRD test results of Example 1 (Fe-Ni3S2@NiCoLDH-300s), Comparative Example 1 (Ni3S2), and Comparative Example 3 (Fe-Ni3S2) are as follows: Figure 17 As shown.

[0069] Analysis: For example Figure 17 As shown, the characteristic diffraction peaks of Example 1 (Fe-Ni3S2@NiCoLDH-300s), Comparative Example 1 (Ni3S2), and Comparative Example 3 (Fe-Ni3S2) all match well with the standard peaks of Ni3S2 (PDF#44-1418) and metallic Ni (PDF#04-0850). The characteristic peaks observed at 21.9°, 31.3°, 37.9°, 49.9°, and 55.3° point to the (101), (110), (003), (113), and (122) planes of Ni3S2, respectively. Notably, compared to pure Ni3S2, the diffraction peaks of Fe-Ni3S2 shift to higher angles, indicating that Fe was successfully doped into the Ni3S2 lattice. Further electrodeposition of NiCo LDH on the surface of the Fe-Ni3S2 precursor did not detect obvious characteristic diffraction peaks of NiCo LDH, which can be attributed to its low crystallinity or ultrathin characteristics.

[0070] To further verify the presence of NiCo LDH in the core-shell material, Raman spectroscopy was performed on Example 1. For comparison, Raman spectroscopy was also performed on Comparative Examples 1, 2, and 3. The Raman spectra of different samples are shown below. Figure 18 As shown.

[0071] The core-shell material Fe-Ni3S2@NiCo LDH exhibits 459 and 527 cm⁻¹. - ¹ Characteristic peaks, which are attributed to two vibrational modes of Ni-O in NiCo LDH, and also at 325 and 351 cm⁻¹ - The typical peak observed at ¹ belongs to the Ni3S2 phase. The coexistence of these different characteristics ultimately confirms the successful synthesis of the Fe-Ni3S2@NiCo LDH core-shell heterostructure. This application provides a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst and its preparation method. The catalyst prepared by this method exhibits excellent activity and stability, and can efficiently electrocatalyze OER under industrial-grade current densities and strong alkaline environments.

[0072] The test results above show that, compared with the comparative examples, the performance advantage of Example 1 (Fe-Ni3S2@NiCoLDH-300s) stems from the synergistic design of its composition and structure: compared with Comparative Example 1 (Ni3S2) and Comparative Example 3 (Fe-Ni3S2) which have no Fe doping and a single active site, Fe doping optimizes the electronic structure and conductivity; compared with Comparative Example 2 (NiCoLDH) which lacks a stable conductive substrate, its three-dimensional core-shell array provides high mechanical strength and charge transport channels; compared with the noble metal reference Comparative Example 4 (RuO2), its cost is significantly reduced and its activity is enhanced; compared with Comparative Example 7 (Fe-Ni3S2@NiLDH) and Comparative Example 8 (Fe-Ni3S2@CoLDH) which lack bimetallic components, the synergistic effect of Ni and Co in the LDH layer enhances the intrinsic activity; in addition, by precisely controlling the deposition time, Example 1 achieves NiCoLDH in Fe- Uniform growth on the Ni3S2 substrate avoids the interfacial inhomogeneities or active site blockage problems that may exist in Comparative Example 6 (NiFe@NiCoLDH). Therefore, this catalyst integrates the electronic regulation of Fe doping, the highly active interface of the core-shell structure, and the synergistic effect of Ni-Co bimetal, thus exhibiting comprehensive and significant improvements in overpotential, reaction kinetics, charge transfer efficiency, and long-term stability.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0074] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst, characterized in that, It includes a conductive nickel substrate and a core-shell electrocatalyst disposed on the surface of the conductive nickel substrate; The core of the core-shell electrocatalyst comprises iron-doped nickel sulfide nanosheets, and the shell comprises nickel-cobalt layered bimetallic hydroxide.

2. The self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 1, characterized in that, The mass ratio of iron, sulfur, cobalt and nickel in the core-shell electrocatalyst is 5-10:10-20:15-25:30-40; And / or, the thickness of the core is 50-60 nm; And / or, the thickness of the shell is 160-170 nm; And / or, the thickness of the core-shell electrocatalyst is 230-240 nm.

3. A method for preparing the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 1 or 2, characterized in that, include: The conductive substrate is pretreated to obtain the pretreated conductive substrate; The pretreated conductive matrix, iron source, and sulfur source are mixed and subjected to a hydrothermal reaction to obtain an iron-modified nickel sulfide nanosheet precursor. The iron-modified nickel sulfide nanosheet precursor, nickel source, cobalt source and water were first mixed and electrodeposited to obtain a self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst.

4. The preparation method of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 3, characterized in that, The pretreatment includes: sequentially subjecting the conductive substrate to solvent ultrasonication, a first water wash, an acid wash, and a second water wash.

5. The preparation method of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 4, characterized in that, The solvent in the solvent ultrasound includes one or more of acetone, ethanol, and isopropanol; And / or, the acid in the pickling includes one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and oxalic acid; The concentration of the acid is 1-6 M; And / or, the solvent is sonicated for 5-30 minutes; And / or, the pickling time is 5-30 min.

6. The preparation method of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 3, characterized in that, The conductive substrate includes one or more of nickel mesh, nickel felt, nickel foam, stainless steel mesh, and carbon paper; And / or, the iron source includes one or more of ferric nitrate, ferric chloride, and ferrous sulfate; And / or, the sulfur source includes one or more of sodium sulfide, thiourea, and thioacetamide; And / or, the nickel source includes one or more of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel aminosulfonate, and nickel fluoroborate; And / or, the cobalt source includes one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt sulfamate, and cobalt fluoroborate.

7. The preparation method of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 3, characterized in that, The molar ratio of the iron source to the sulfur source is 0.6-1.2:2-5; And / or, the molar ratio of the nickel source to the cobalt source is 1-3:1-3.

8. The preparation method of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 3, characterized in that, The hydrothermal reaction is carried out at a temperature of 120-180℃ for 4-8 hours.

9. The preparation method of the self-supported Fe-Ni3S2@NiCoLDH core-shell electrocatalyst according to claim 3, characterized in that, The electrodeposition voltage is -0.8V to -1.2V, the temperature is room temperature, and the time is 50-800s.

10. A method for producing hydrogen, characterized in that, This includes using the self-supporting Fe-Ni3S2@NiCoLDH core-shell electrocatalyst as described in claim 1 or 2 as an anode for hydrogen production via water electrolysis.

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