Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites, their preparation methods, and applications.

Abstract

The present application relates to the technical field of electrode material, in particular to Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material and its preparation method and application. The present application takes soluble manganese salt and soluble cobalt salt as raw materials, takes foam nickel as carrier, carries out hydrothermal reaction under alkaline environment to obtain MnCo-LDH / NF, then immerses MnCo-LDH / NF in a precursor solution composed of soluble cobalt salt and 2-methyl imidazole, and carries out coordination reaction to obtain MnCo-LDH@ZIF-67 / NF, finally adopts thioacetamide to incompletely sulfide MnCo-LDH@ZIF-67 / NF to obtain Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material. Through Co3S4 and MnCo-LDH, the technical defects existing in MnCo2S4 are overcome.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, specifically to Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite materials, their preparation methods, and applications. Background Technology

[0002] Transition metal sulfides are considered promising electrode materials due to their abundant redox sites and superior conductivity compared to their corresponding metal oxides. Compared to single-metal sulfides, mixed metal sulfides, by introducing heterometallic ions, can enhance charge transfer between different ions and alter the electronic structure, thereby lowering the kinetic barrier of the electrochemical process. Co-based ZIFs are widely used as electrode materials because of the redox properties of the cobalt active sites, where cobalt readily undergoes electron transfer between multiple oxidation states from +1 to +4 during the reaction. Furthermore, the valence electron structure of Co is [3d...]. 7 4s 2 Therefore, when it chelates with different molecular ligands, it has a high coordination number, which is beneficial for synthesizing high-performance Co-based metal-organic framework materials while maintaining the desired chemical stability. In particular, ZIF derivatives can retain roughly the original morphology, have a high specific surface area, and can provide abundant active sites with enhanced charge transfer.

[0003] MnCo2S4, as an electrode material for hydrogen production through water electrolysis, has advantages such as good rate performance, excellent cycle stability, and diverse crystal structures, resulting in excellent conductivity and energy storage efficiency. However, its insufficient conductivity, poor structural stability, slow redox reaction rate, and limited number of active sites limit its widespread application. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention provides a Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material, its preparation method, and its applications. This invention uses soluble manganese salt and soluble cobalt salt as raw materials, and nickel foam as a carrier. A hydrothermal reaction is carried out under alkaline conditions to obtain MnCo-LDH / NF. Then, MnCo-LDH / NF is immersed in a precursor solution composed of soluble cobalt salt and 2-methylimidazole, and a coordination reaction is performed to obtain MnCo-LDH@ZIF-67 / NF. Finally, MnCo-LDH@ZIF-67 / NF is vulcanized with thioacetamide to obtain the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material. In the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material obtained by the method of the present invention, the nanorod-shaped MnCo2S4 and the dodecahedral Co3S4 form a heterojunction, and the technical defects of MnCo2S4 are overcome by Co3S4 and MnCo-LDH.

[0005] Based on the above technical objectives, the present invention adopts the following technical solution:

[0006] This invention protects a method for preparing Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites, comprising the following steps:

[0007] Soluble manganese salt, soluble cobalt salt, urea and ammonium fluoride are mixed together in water to obtain a mixture. Nickel foam is immersed in the mixture and subjected to a hydrothermal reaction to obtain MnCo-LDH / NF.

[0008] Using soluble cobalt salt and 2-methylimidazole as raw materials, the two were dispersed separately in a solvent and then mixed evenly to obtain a precursor solution; MnCo-LDH / NF was then immersed in the precursor solution to carry out a coordination reaction to obtain MnCo-LDH@ZIF-67 / NF.

[0009] MnCo-LDH@ZIF-67 / NF was immersed in a thioacetamide alcohol solution and subjected to a hydrothermal reaction to obtain a Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material.

[0010] Preferably, MnCo-LDH@ZIF-67 / NF is immersed in a thioacetamide alcohol solution, and the hydrothermal reaction conditions are: heating at 100°C~160°C for 2h~6h.

[0011] Preferably, the amount of thioacetamide in the thioacetamide alcohol solution is 1 mmol to 3 mmol.

[0012] Preferably, the molar ratio of soluble manganese salt, soluble cobalt salt, urea and ammonium fluoride is 0.5:0.8~1.2:6:1.5~3.

[0013] Preferably, the hydrothermal reaction conditions during the preparation of MnCo-LDH / NF are: heating at 100°C to 140°C for 8 to 12 hours.

[0014] Preferably, the amount of soluble cobalt salt in the precursor solution is 0.8 mmol to 1.2 mmol.

[0015] Preferably, the conditions for the coordination reaction are: standing at room temperature for 24h~36h.

[0016] This invention also protects the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material, which is prepared by the above-described method.

[0017] This invention also protects the application of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite materials in the preparation of electrocatalytic hydrogen production electrode materials.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. This invention successfully synthesized a Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material derived from LDH and ZIF as sacrificial templates on nickel foam through hydrothermal and sulfidation treatment. The invention first used soluble manganese salt, soluble cobalt salt, urea, ammonium fluoride, and nickel foam as raw materials, wherein urea and ammonium fluoride jointly provided an alkaline environment. After hydrothermal reaction, a layered MnCo bimetallic hydroxide, namely MnCo-LDH, was obtained and stably bonded to the nickel foam, yielding MnCo-LDH / NF. A precursor solution was prepared using soluble cobalt salt and 2-methylimidazole as raw materials. MnCo-LDH / NF was immersed in the precursor solution, and cobalt ions reacted with 2-... Methylimidazole undergoes a coordination reaction, during which ZIF-67 grows on MnCo layered bimetallic hydroxide to obtain MnCo-LDH@ZIF-67 / NF. MnCo-LDH@ZIF-67 / NF is then mixed with a thioacetamide alcohol solution and subjected to a hydrothermal reaction. The hydrothermal process achieves incomplete sulfidation of MnCo layered bimetallic hydroxide and ZIF-67, resulting in a Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material.

[0020] 2. In the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material of the present invention, Co3S4 and MnCo2S4, as sulfides, have excellent electrical conductivity, and the layered structure of MnCo-LDH provides abundant active sites, allowing electrons to transfer between these components, thereby optimizing the charge distribution. The nanostructures of Co3S4 and MnCo2S4 can form good interfacial contact with the layered structure of MnCo-LDH. This interfacial contact enhances the binding force between the components through physical adsorption or chemical bonding. As sulfides, Co3S4 and MnCo2S4 have high specific surface area and active sites, and the layered structure of MnCo-LDH provides additional adsorption and catalytic sites. This structural synergy optimizes the overall performance of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material.

[0021] Furthermore, in this invention, Co3S4 and MnCo2S4 form a heterojunction. The synergistic effect between Co3S4 and MnCo2S4 can significantly improve the energy density, rate performance, and cycle stability of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material. The charge redistribution at the interface of the heterojunction creates a built-in electric field, accelerating the transport of electrons and ions. The heterojunction structure can expose more active sites, thereby improving the efficiency of the catalytic reaction.

[0022] 3. The Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material of the present invention exhibits excellent UOR and EOR performance in electrocatalytic water electrolysis for hydrogen production. The OER potential is 1.551V, the UOR potential is 1.37V, and the EOR potential is 1.379V. Compared with the OER potential, the UOR performance is significantly improved at 10mA / cm². 2 At the specified current density, the UOR potential and EOR potential decreased by 181 mV and 172 mV, respectively. Furthermore, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material exhibited stability in hydrogen production, and the electrolyzer assembled using the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material as both the anode and cathode also demonstrated good catalytic performance.

[0023] In summary, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material of the present invention is an energy-saving and efficient hydrogen production electrode material with good practical application prospects.

[0024] 4. This invention synthesizes Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites on nickel foam using an improved metal-organic framework template-guided strategy. By combining ZIF-67 dodecahedrons with CoMn-LDH nanowires, a MnCo-LDH@ZIF-67 composite material is obtained. Specifically, these LDH nanowires are grown on nickel foam and form an array structure, which facilitates ion diffusion and electron transfer. Furthermore, compared to MnCo-LDH and MnCo-LDH@ZIF-67, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites exhibit improved performance as an electrocatalyst for oxygen precipitation reactions. Moreover, in an alkaline electrolyte with added urea, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites maintain good stability; the excellent catalytic performance is attributed to the synergistic effect of the active substances MnCo-LDH, MnCo2S4, and Co3S4.

[0025] In this invention, LDH represents layered bimetallic hydroxide, UOR represents urea oxidation reaction, urea represents urea, EOR represents ethanol oxidation reaction, OER represents oxygen evolution reaction, CV represents cyclic voltammetry, GCD represents constant current rapid charge-discharge, EIS represents electrochemical impedance spectroscopy, SEM represents scanning electron microscopy, TEM represents transmission electron microscopy, XRD represents X-ray diffraction, XPS represents X-ray photoelectron spectroscopy, HRTEM represents high-resolution transmission electron microscopy, EDS represents energy-dispersive X-ray spectroscopy, and C... dl This indicates a double-layer capacitor, and ECSA represents the active surface area. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the synthesis of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material of the present invention.

[0027] Figure 2 Figure a shows the XRD patterns of MnCo-LDH from Example 1, MnCo-LDH@ZIF-67 from Example 1, and ZIF-67 from Comparative Example 1; Figure b shows the XRD patterns of S-100-4 from Example 1, S-60-4 from Comparative Example 2, and S-80-4 from Comparative Example 3; Figure c shows the full XPS spectrum of S-100-4 from Example 1; Figure d shows the XPS spectrum of Co 2p from S-100-4 from Example 1; Figure e shows the XPS spectrum of Mn 2p from S-100-4 from Example 1; Figure f shows the XPS spectrum of S 2p from S-100-4 from Example 1.

[0028] Figure 3Figures are electron microscope images; where, Figure a is the SEM image of MnCo-LDH in Example 1; Figures b and c are the SEM images of MnCo-LDH@ZIF-67 in Example 1 at different magnifications; Figures d to f are the SEM images of S-100-4 in Example 1 at different magnifications; Figures g and h are the TEM images of S-100-4 in Example 1 at different angles; Figure i is the HRTEM image of S-100-4 in Example 1.

[0029] Figure 4 The image shows the EDS diagram of S-100-4 in Example 1.

[0030] Figure 5 In the figures, Figures a to c show the electrochemical performance of S-100-4 from Example 1, S-60-4 from Comparative Example 2, and S-80-4 from Comparative Example 3, where Figure a is the CV curve, Figure b is the GCD curve, and Figure c is the EIS curve; Figures d to f show the electrochemical performance of S-100-4 from Example 1, S-100-0.5 from Comparative Example 4, and S-100-1 from Comparative Example 5, where Figure d is the CV curve, Figure e is the GCD curve, and Figure f is the EIS curve.

[0031] Figure 6 The figures show the electrochemical performance of MnCo-LDH from Example 1, MnCo-LDH@ZIF-67 from Example 1, and S-100-4 from Example 1 in 1.0 mol / L KOH + 0.3 mol / L urea electrolyte. Figure a is the UOR curve, figure b is the UOR-Tafel curve, figure c is the HER curve, and figure d is the HER-Tafel curve.

[0032] Figure 7 Figures a through d show the electrochemical performance of MnCo-LDH, MnCo-LDH@ZIF-67, and S-100-4 from Example 1 in 1.0 mol / L KOH electrolyte. Figure a is the UOR curve, figure b is the UOR-Tafel curve, figure c is the HER curve, and figure d is the HER-Tafel curve. Figures e through h show the electrochemical performance of MnCo-LDH, MnCo-LDH@ZIF-67, and S-100-4 from Example 1 in 1.0 mol / L KOH + 0.3 mol / L ethanol electrolyte. Figure e is the UOR curve, figure f is the UOR-Tafel curve, figure g is the HER curve, and figure h is the HER-Tafel curve.

[0033] Figure 8Figure a shows the CV curves of MnCo-LDH in Example 1 at different scan rates; Figure b shows the CV curves of MnCo-LDH@ZIF-67 in Example 1 at different scan rates; Figure c shows the CV curves of S-100-4 in Example 1 in the non-Radida potential range at different scan rates; and Figure d shows the double-layer capacitance diagrams of MnCo-LDH, MnCo-LDH@ZIF-67, and S-100-4 in Example 1.

[0034] Figure 9 Figures a through d show the curves of S-100-4 from Example 1 in 1.0 mol / L KOH, 1.0 mol / L KOH + 0.3 mol / L urea, and 1.0 mol / L KOH + 0.3 mol / L ethanol electrolytes, respectively. Figure a is the LSV polarization curve, figure b is the Tafel slope curve, figure c is the HER polarization curve, and figure d is the HER-Tafel curve. Figure e is the it curve of S-100-4 from Example 1 in 1.0 mol / L KOH + 0.3 mol / L urea electrolyte. Figure f is the SEM image of S-100-4 from Example 1 after the it test in 1.0 mol / L KOH + 0.3 mol / L urea electrolyte.

[0035] Figure 10 Figure a shows a photograph of the S-100-4 / / Pt dual-electrode battery assembled using S-100-4 and Pt sheets from Example 1, along with a 1.0 mol / L KOH + 0.3 mol / L urea electrolyte. Figure b shows the LSV polarization curves of the S-100-4 / / Pt dual-electrode battery in 1.0 mol / L KOH, 1.0 mol / L KOH + 0.3 mol / L urea, and 1.0 mol / L KOH + 0.3 mol / L ethanol electrolytes, respectively. Figure c shows the LSV polarization curves at 10 mA / cm². 2 Figure d shows a comparison of the overpotential of S-100-4 from Example 1 with existing catalytic materials at the current density; Figure d is a physical image of S-100-4 / / S-100-4 assembled with S-100-4 from Example 1 as the anode and cathode and 1.0 mol / L KOH + 0.3 mol / L urea electrolyte; Figure e shows the LSV polarization curves of S-100-4 / / S-100-4 in 1.0 mol / L KOH, 1.0 mol / L KOH + 0.3 mol / L urea, and 1.0 mol / L KOH + 0.3 mol / L ethanol electrolytes. Detailed Implementation

[0036] The technical solution of the present invention will be described more clearly and completely below with reference to specific embodiments. The described embodiments are only some embodiments of the present invention, and not all of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0037] Example 1

[0038] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite materials includes the following steps:

[0039] Preparation of S1 and MnCo-LDH: Weigh 125 mg manganese nitrate tetrahydrate, 291 mg cobalt nitrate hexahydrate, 360 mg urea and 92.5 mg ammonium fluoride respectively, and then dissolve them together in a beaker containing 35 mL of distilled water. Stir magnetically for 15 min to form a homogeneous mixture. Immerse a piece of treated 1 cm × 2 cm nickel foam into the mixture, and then transfer it to a 50 mL autoclave. Heat it in an oven at 100°C for 9 h. After cooling to room temperature, remove it to obtain MnCo-LDH / NF. Wash it 4 times with deionized water and dry it at 70°C for later use.

[0040] Preparation of S2 and MnCo-LDH@ZIF-67: 291 mg of cobalt nitrate hexahydrate was dissolved in 25 mL of methanol to obtain a cobalt salt solution; 656 mg of 2-methylimidazole was dissolved in 25 mL of methanol to form a clear solution to obtain a ligand solution; the ligand solution was poured into the cobalt salt solution to form a precursor solution; a piece of MnCo-LDH / NF was immersed in the precursor solution and allowed to stand at room temperature for 24 h to obtain MnCo-LDH@ZIF-67 / NF; the obtained MnCo-LDH@ZIF-67 / NF was washed with methanol and dried at 70°C for 12 h for later use.

[0041] Preparation of S3, Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites: MnCo-LDH@ZIF-67 / NF was immersed in a methanol solution containing 120 mg of thioacetamide (40 mL volume), then transferred to a 50 mL autoclave and heated at 100°C for 4 h. After cooling to room temperature, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites were obtained. The nanocomposites were washed three times with ethanol and dried at 70°C for 12 h, and designated as S-100-4.

[0042] Example 2

[0043] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite materials includes the following steps:

[0044] Preparation of S1 and MnCo-LDH: Weigh 125 mg manganese nitrate tetrahydrate, 233 mg cobalt nitrate hexahydrate, 360 mg urea and 55.5 mg ammonium fluoride respectively, and then dissolve them together in a beaker containing 35 mL of distilled water. Stir magnetically for 15 min to form a homogeneous mixture. Immerse a piece of treated 1 cm × 2 cm nickel foam into the mixture, then transfer it to a 50 mL autoclave and heat it in an oven at 100°C for 12 h. After cooling to room temperature, remove it to obtain MnCo-LDH / NF. Wash it 4 times with deionized water and dry it at 70°C for later use.

[0045] Preparation of S2 and MnCo-LDH@ZIF-67: 233 mg of cobalt nitrate hexahydrate was dissolved in 25 mL of methanol to obtain a cobalt salt solution; 656 mg of 2-methylimidazole was dissolved in 25 mL of methanol to form a clear solution to obtain a ligand solution; the ligand solution was poured into the cobalt salt solution to form a precursor solution; a piece of MnCo-LDH / NF was immersed in the precursor solution and allowed to stand at room temperature for 30 h to obtain MnCo-LDH@ZIF-67 / NF; the obtained MnCo-LDH@ZIF-67 / NF was washed with methanol and dried at 70°C for 12 h for later use.

[0046] Preparation of S3, Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites: MnCo-LDH@ZIF-67 / NF was immersed in a methanol solution containing 60 mg of thioacetamide (40 mL volume), then transferred to a 50 mL autoclave and heated at 120°C for 6 h. After cooling to room temperature, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites were obtained. The nanocomposites were rinsed three times with ethanol and dried at 70°C for 12 h.

[0047] Example 3

[0048] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite materials includes the following steps:

[0049] Preparation of MnCo-LDH: Weigh 125 mg manganese nitrate tetrahydrate, 349 mg cobalt nitrate hexahydrate, 360 mg urea and 111 mg ammonium fluoride respectively, and then dissolve them together in a beaker containing 35 mL of distilled water. Stir magnetically for 15 min to form a homogeneous mixture. Immerse a piece of treated 1 cm × 2 cm nickel foam into the mixture, then transfer it to a 50 mL autoclave and heat it in an oven at 140°C for 8 h. After cooling to room temperature, remove it to obtain MnCo-LDH / NF. Wash it 4 times with deionized water and dry it at 70°C for later use.

[0050] Preparation of S2 and MnCo-LDH@ZIF-67: 349 mg of cobalt nitrate hexahydrate was dissolved in 25 mL of methanol to obtain a cobalt salt solution; 656 mg of 2-methylimidazole was dissolved in 25 mL of methanol to form a clear solution to obtain a ligand solution; the ligand solution was poured into the cobalt salt solution to form a precursor solution; a piece of MnCo-LDH / NF was immersed in the precursor solution and allowed to stand at room temperature for 36 h to obtain MnCo-LDH@ZIF-67 / NF; the obtained MnCo-LDH@ZIF-67 / NF was washed with methanol and dried at 70°C for 12 h for later use.

[0051] Preparation of S3, Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites: MnCo-LDH@ZIF-67 / NF was immersed in a methanol solution containing 180 mg of thioacetamide (40 mL volume), then transferred to a 50 mL autoclave and heated at 160°C for 2 h. After cooling to room temperature, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites were obtained. The nanocomposites were rinsed three times with ethanol and dried at 70°C for 12 h.

[0052] Example 4

[0053] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material is the same as that in Example 1, except that the temperature of the hydrothermal method in step S3 is replaced by 120°C instead of 100°C, denoted as S-120-4.

[0054] Comparative Example 1

[0055] The preparation method of ZIF-67 includes the following steps:

[0056] 291 mg of cobalt nitrate hexahydrate was dissolved in 25 mL of methanol to obtain solution A; 656 mg of 2-methylimidazole was dissolved in 25 mL of methanol to form a clear solution to obtain solution B; solution B was poured into solution A and allowed to stand at room temperature for 24 h to obtain ZIF-67.

[0057] Comparative Example 2

[0058] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material is the same as that in Example 1, except that the temperature of the hydrothermal method in step S3 is replaced by 60°C instead of 100°C, which is denoted as S-60-4.

[0059] Comparative Example 3

[0060] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material is the same as that in Example 1, except that the temperature of the hydrothermal method in step S3 is replaced by 80°C instead of 100°C, which is denoted as S-80-4.

[0061] Comparative Example 4

[0062] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material is the same as that in Example 1, except that the hydrothermal method time in step S3 is replaced by 0.5h instead of 4h, denoted as S-100-0.5.

[0063] Comparative Example 5

[0064] The preparation method of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material is the same as that in Example 1, except that the hydrothermal method time in step S3 is replaced by 1 hour instead of 4 hours, denoted as S-100-1.

[0065] Examples 1 to 3 of this invention all yielded Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites with excellent electrochemical properties. The following research uses the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites from Example 1 and Comparative Examples 1 to 5 as examples. Specific research methods and results are shown below:

[0066] The synthesis scheme of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites is as follows: Figure 1 As shown, firstly, a uniform MnCo-LDH was synthesized on nickel foam using a simple hydrothermal method; then, MnCo-LDH@ZIF-67 was synthesized by static curing at room temperature; finally, incomplete vulcanization of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material was achieved using a hydrothermal method.

[0067] 1. Morphology and structural characterization of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites:

[0068] The XRD patterns of MnCo-LDH, ZIF-67, and MnCo-LDH@ZIF-67 are as follows: Figure 2 As shown in Figure a, the peaks correspond well to the PDF cards. The weak peaks in MnCo-LDH and MnCo-LDH@ZIF-67 are attributed to the intensity of the Ni peak. The XRD patterns of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites under different sulfidation conditions are shown below. Figure 2As shown in Figure b, a diffraction peak belonging to MnCo-LDH is still observed near 12°, corresponding to the (003) crystal plane, proving the incomplete sulfurization of MnCo-LDH. S-80-4 does not show a significant diffraction peak, possibly because the loading is too high, resulting in an excessive thickness of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite. The weak peak at 20.3° is attributed to the (080) crystal plane of sulfur (JCPDS No. 24-1251), which is caused by the decomposition of thioacetamide. Diffraction peaks are located at 33.7° and 38.7°, corresponding to the (222) and (400) crystal planes of Co3S4, respectively. The diffraction peaks of MnCo2S4 are similar to those of Co3S4 because the structure of MnCo2S4 is roughly that some Co ions are replaced by Mn ions while maintaining the original crystal structure, and only the lattice parameters are slightly changed. The structure of MnCo2S4 will be analyzed by XPS and EDS later.

[0069] To further investigate the valence states of the chemical constituent elements in the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material, X-ray photoelectron spectroscopy (XPS) measurements were performed. The results are shown in... Figure 2 c~ Figure 2 f in. The full spectrum is as follows: Figure 2 As shown in Figure c, the peaks corresponding to Mn, Co, and S are visible. The energy spectrum of Co 2p is as follows. Figure 2 As shown in the d-figure, Co 3+ The binding energies are located at 779.4 eV and 794.4 eV, respectively. 2+ The binding energies are located at 781.4 eV and 797.3 eV, respectively; in addition, two satellite companion peaks can be observed. The energy spectrum of Mn 2p is as follows: Figure 2 As shown in the d-plot, the binding energies at 638 eV, 642.4 eV, and 644.7 eV are fitted to Mn2p. 3 / 2 The peaks represent Mn, respectively. 2+ Mn 3+ and Mn 4+ The oxidation state of Mn2p is shown by fitting. 1 / 2 The peaks are at 653.2 eV and 654.2 eV, which belong to Mn, respectively. 2+ and Mn 3+ The energy spectrum of S 2p is as follows: Figure 2 As shown in the f-plot, two peaks are observed at 162.6 eV and 164 eV, corresponding to S 2p, respectively. 3 / 2 and S 2p 1 / 2 .

[0070] The morphology and structure of the samples prepared in each step were characterized using SEM and TEM, such as... Figure 3 As shown, Figure 3 As shown in Figure a, MnCo-LDH nanoneedles are uniformly and densely grown on a nickel foam substrate. Figure 3 Figure b in the middle and Figure 3 In Figure c, well-crystallized ZIF-67 crystals with uniform size and shape are observed. Clearly, the ZIF-67 crystals are rhombic dodecahedral in shape and grow around MnCo-LDH nanowires. SEM images of S-100-4 are shown below. Figure 3 d~ Figure 3 In the f-section, after sulfurization treatment, MnCo-LDH-derived MnCo2S4 and ZIF-67-derived Co3S4 retain similar nanorod and dodecahedral shapes, respectively, and both surfaces become roughened. Typical TEM images of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites are shown below. Figure 3 g~ Figure 3 As shown in h, the structure of nanorods and polyhedra is presented more clearly, further confirming the synthesis of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material. Figure 3 As shown in Figure i, a lattice spacing of 0.21 nm corresponds to the (400) plane of MnCo2S4, and a lattice spacing of 0.25 nm is assigned to the (018) plane of MnCo-LDH, further verifying the incomplete sulfidation of MnCo-LDH and the synthesis of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites. A lattice spacing of 0.26 nm corresponds to the (400) plane of Co3S4. In particular, there are obvious interfaces between MnCo-LDH and Co3S4, MnCo-LDH and MnCo2S4, and Co3S4 and MnCo2S4. In addition, amorphous phases, such as..., were also detected at the interfaces. Figure 3 The I marked in i also proves that heterojunctions are formed between MnCo-LDH and Co3S4, MnCo-LDH and MnCo2S4, and Co3S4 and MnCo2S4.

[0071] from Figure 4 The EDS spectrum of S-100-4 shows that Mn, Co and S elements are uniformly distributed in the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material.

[0072] 2. Electrochemical properties of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites:

[0073] In this invention, the CV curve, GCD curve, and EIS curve are all measured using a three-electrode system. A saturated calomel electrode is used as the reference electrode, and a Pt sheet is used as the counter electrode. Together with the working electrode, they form a three-electrode system. The working electrode is prepared by mixing the catalyst material, conductive agent, binder, and solvent and then loading them onto the current collector. The catalyst material is the material synthesized in this invention, and the mass ratio of the catalyst material, conductive agent, and binder is 8:1:1.

[0074] To further investigate the electrochemical properties of Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites under different degrees of sulfidation, two axes were compared for different sulfidation temperatures and times. Figure 5 a~ Figure 5 c shows the electrochemical performance at different sulfidation temperatures. Figure 5 d~ Figure 5 f(x) shows the electrochemical properties at different sulfidation times. Cyclic voltammetry and charge-discharge curves show that the performance of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite improves with increasing sulfidation temperature. Figure 5 c and Figure 5 As can be seen, S-100-4 has lower mass transfer resistance and better ionic conductivity compared with other samples.

[0075] The catalytic activities of MnCo-LDH, MnCo-LDH@ZIF-67, and S-100-4 samples were investigated in a three-electrode system in 1.0 mol / L KOH, 1.0 mol / L KOH + 0.3 mol / L urea, and 1.0 mol / L KOH + 0.3 mol / L C2H5OH electrolytes, respectively. Figure 6 and Figure 7 As shown. Figure 6 The catalytic performance of the three substances was compared in a 1.0 mol / L KOH + 0.3 mol / L urea electrolyte solution. Figure 6 a~ Figure 6 Figure b shows the UOR performance and Tafel slope of the three samples. The S-100-4 can reach 10 mA / cm² with only 1.37 V. 2 MnCo-LDH requires 1.463V, MnCo-LDH@ZIF-67 requires 1.41V, and S-100-4 reaches 10mA / cm. 2The voltage of S-100-4 is lower than that of MnCo-LDH and MnCo-LDH@ZIF-67. Furthermore, the Tafel slopes of S-100-4, MnCo-LDH, and MnCo-LDH@ZIF-67 are 85 mV / dec, 127 mV / dec, and 119 mV / dec, respectively. The Tafel slope of S-100-4 is much smaller than that of MnCo-LDH and MnCo-LDH@ZIF-67, indicating better UOR catalytic performance and more favorable kinetic properties. Figure 6 c~ Figure 6 d shows the HER curves of three samples at 100 mA / cm². 2 At current densities, the required overpotentials for S-100-4, MnCo-LDH, and MnCo-LDH@ZIF-67 are 420mV, 490mV, and 500mV, respectively. The Tafel slope of S-100-4 is 141mV / dec, which is much smaller than that of MnCo-LDH and MnCo-LDH@ZIF-67. The Tafel slope of MnCo-LDH is 169mV / dec, and the Tafel slope of MnCo-LDH@ZIF-67 is 152mV / dec. Figure 7 As can be seen, the same trend is observed in 1.0 mol / L KOH and 1.0 mol / L KOH + 0.3 mol / L C2H5OH electrolytes. Comparing the performance of S-100-4 with MnCo-LDH and MnCo-LDH@ZIF-67 in the three electrolytes, it is obvious that the catalytic activity of S-100-4 is better than that of the matrix MnCo-LDH and MnCo-LDH@ZIF-67. The reason is that the new interface provides more reactive sites.

[0076] To investigate the electrochemically active surface area of ​​Co3S4 / MnCo-LDH / MnCo2S4 nanocomposites, this invention uses cyclic voltammetry to measure CV curves, and measures the double-layer capacitance CV of MnCo-LDH, MnCo-LDH@ZIF-67, and S-100-4 in the non-Radar potential region at different scan rates. dl The voltage in the non-Radar potential region is 0V~0.1V, to estimate the electrochemical active surface area of ​​MnCo-LDH, MnCo-LDH@ZIF-67 and S-100-4, such as... Figure 8 a~ Figure 8 As shown in Figure c, this is due to the electrochemically active surface area and the double-layer capacitance C. dl Linear correlation. For example... Figure 7 As shown in Figure d, the double-layer capacitor C of S-100-4 dl The value is 7.7 mF / cm 2The capacitance C of MnCo-LDH is much larger than that of MnCo-LDH and MnCo-LDH@ZIF-67. dl The value is 1.56 mF / cm 2 MnCo-LDH@ZIF-67 double-layer capacitor C dl The value is 2.5 mF / cm 2 This demonstrates that the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite has more active sites than the matrix MnCo-LDH and MnCo-LDH@ZIF-67.

[0077] Figure 9 Figure a shows the LSV polarization curves of S-100-4 in the three electrolytes, clearly demonstrating that UOR and EOR have significant advantages compared to OER. OER requires a potential of 1.551V to achieve 10mA / cm. 2 The current density is significantly higher in the solution than in the solution containing urea. With the addition of urea, the UOR (hydrogen regeneration) requires only 1.37V, while in the solution containing ethanol, the EOR (hydrogen regeneration) requires 1.379V. Therefore, the addition of urea and ethanol effectively improves hydrogen production efficiency. Figure 9 Figure b shows the Tafel slopes of S-100-4 in the three electrolytes, reflecting the reaction kinetics. The Tafel slopes of S-100-4 in 1.0 mol / L KOH, 1.0 mol / L KOH + 0.3 mol / L urea, and 1.0 mol / L KOH + 0.3 mol / L C2H5OH electrolytes are 101 mV / dec, 85 mV / dec, and 86 mV / dec, respectively. The addition of urea significantly promoted the kinetic behavior of the reaction. Figure 9 Figure c shows the HER polarization curves. In the electrolyte with added urea, the overpotential at the same current density is consistently lower than that in 1.0 mol / L KOH and 1.0 mol / L KOH + 0.3 mol / L C2H5OH, where the potentials are 419 mV, 440 mV, and 458 mV respectively, to provide 100 mA / cm². 2 The current density. Figure 9 The d-plot shows the Tafel slopes of S-100-4 in three electrolytes. The Tafel slopes of S-100-4 in 1.0 mol / L KOH, 1.0 mol / L KOH + 0.3 mol / L urea, and 1.0 mol / L KOH + 0.3 mol / L C2H5OH electrolytes are 141 mV / dec, 141 mV / dec, and 148 mV / dec, respectively, indicating that the addition of urea and ethanol does not have much negative impact on HER. To investigate the catalytic stability of S-100-4, it was tested using a three-electrode system, such as... Figure 9As shown in Figure e, the results indicate that the current density of S-100-4 remains stable at 170 mA / cm² within 24 hours. 2 The slight increase in the first 6 hours may be due to the activation process of S-100-4. Figure 9 Figure f in the figure shows the SEM image after 24h of IT testing. S-100-4 remains a nanostructure, and the structure does not show excessive collapse or damage, exhibiting good catalytic stability.

[0078] Because the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material exhibits excellent performance in catalytic water splitting for hydrogen production, this invention configures a dual-electrode battery in a 1.0 mol / L KOH + 0.3 mol / L urea electrolyte, such as... Figure 10 As shown in Figure a, the practical application of the catalytic performance of S-100-4 is studied using S-100-4 as the positive electrode and Pt as the negative electrode. The Pt electrode on the left performs the HER process to produce H2, while the S-100-4 on the right performs the UOR reaction process to produce N2 and CO2. Figure 10 Figure b shows the LSV curves of S-100-4 / / Pt in the three electrolytes, and it can be noted that UOR has a significant advantage over EOR and OER. To obtain 10 mA / cm... 2 With a current density of only 1.519V, UOR requires only 1.519V, which is much smaller than EOR and OER, which require 1.925V and 1.753V respectively. Figure 10 Figure c in the figure compares the results of this invention with some other most recently reported catalytic materials, demonstrating that at the same 10 mA / cm², the results are comparable to those of other catalytic materials. 2 At the specified current density, the S-100-4 of this invention exhibits a low overpotential. Furthermore, this invention constructed electrolytic cells using S-100-4 as both anode and cathode in three different electrolyte solutions to further investigate the practical application of S-100-4 in H2 production. Figure 10 The image shown in Figure d is a picture taken under 1.0 mol / L KOH + 0.3 mol / L urea electrolyte. It is clear that abundant bubbles are observed on the surface of S-100-4. Figure 10 The figure shows the LSV curves of S-100-4 / / S-100-4 in three different electrolytes at 10 mA / cm. 2 At the given current density, the potentials in the three electrolytes are 1.716V, 1.532V, and 1.63V, respectively.

[0079] For the UOR process used in energy-efficient hydrogen production, CO(NH2)2 is oxidized and reacts with OH... - The reaction involves the loss of electrons, producing carbon dioxide, nitrogen, and water. The reaction equation is: CO(NH2)2 + 6OH-- ↔CO2 + N2 + 5H2O + 6e - In this invention, the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material provides an excellent pathway for the electrochemical reaction in the UOR process. First, MnCo-LDH nanoneedles were directly prepared on nickel foam, exhibiting good conductivity and facilitating rapid electron migration during the electrochemical reaction. Second, the growth of numerous Co3S4 polyhedral particles on the MnCo2S4 / MnCo-LDH nanoneedles demonstrates a synergistic effect, resulting in more reactive sites on the surface of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material and multi-channel ion transport, effectively improving the electrochemical performance of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material.

[0080] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A method for preparing Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite materials, characterized in that, Includes the following steps: Soluble manganese salt, soluble cobalt salt, urea and ammonium fluoride are mixed together in water to obtain a mixture. Nickel foam is immersed in the mixture and subjected to a hydrothermal reaction to obtain MnCo-LDH / NF. During the preparation of MnCo-LDH / NF, the hydrothermal reaction conditions are: heating at 100°C~140°C for 8h~12h; The molar ratio of soluble manganese salt, soluble cobalt salt, urea and ammonium fluoride is 0.5:0.8~1.2:6:1.5~3; Using soluble cobalt salt and 2-methylimidazole as raw materials, the two were dispersed separately in a solvent and then mixed evenly to obtain a precursor solution; MnCo-LDH / NF was then immersed in the precursor solution to carry out a coordination reaction to obtain MnCo-LDH@ZIF-67 / NF. The amount of soluble cobalt salt in the precursor solution is 0.8 mmol to 1.2 mmol. MnCo-LDH@ZIF-67 / NF was immersed in a thioacetamide alcohol solution and subjected to a hydrothermal reaction. The hydrothermal reaction conditions were: heating at 100°C~160°C for 2h~6h to obtain Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material. In the thioacetamide alcohol solution, the amount of thioacetamide is 1 mmol to 3 mmol.

2. The method for preparing the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material according to claim 1, characterized in that, The conditions for the coordination reaction are: standing at room temperature for 24-36 hours.

3. A Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 2.

4. The application of the Co3S4 / MnCo-LDH / MnCo2S4 nanocomposite material as described in claim 3 in the preparation of electrode materials for electrocatalytic water electrolysis to produce hydrogen.

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