A method for preparing a coated V-doped Ni3S2 core-shell structure
By doping nickel sulfides with vanadium to form a coated V-doped Ni3S2 core-shell structure, the problem of slow charge transfer during water electrolysis was solved, achieving highly efficient water electrolysis catalytic performance and long-term stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENAN AGRICULTURAL UNIVERSITY
- Filing Date
- 2023-01-10
- Publication Date
- 2026-08-04
AI Technical Summary
Existing nickel sulfide catalysts suffer from slow charge transfer during water electrolysis, resulting in low hydrogen production efficiency. Therefore, it is necessary to develop bifunctional catalysts with high activity and stability.
By doping nickel sulfide with vanadium to form a coated V-doped Ni3S2 core-shell structure, the morphology and electronic structure of the catalyst are controlled, the exposure of active sites is increased, and nanosheets are directly grown on nickel foam by electrodeposition to form a three-dimensional core-shell structure.
It improves the charge transport efficiency and stability of the catalyst, promotes the transport and diffusion of electrolyte ions, enhances the catalytic activity and reaction kinetics of water electrolysis, and achieves excellent electrochemical hydrogen and oxygen evolution performance and long-term stability.
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Figure CN115928138B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water electrolysis catalyst technology, specifically relating to a method for preparing a three-dimensional core-shell composite material, particularly a method for preparing a V-doped Ni3S2 core-shell composite material, and the application of the composite material in the water electrolysis reaction. Background Technology
[0002] Hydrogen is a clean and sustainable energy carrier. Due to its zero carbon emissions and high energy density, its combined application with renewable energy sources holds promise for alleviating the energy crisis and environmental problems. Water electrolysis driven by renewable energy is an environmentally friendly and sustainable method for hydrogen production. However, the anodic reaction (OER) and cathodic reaction (HER) in water electrolysis involve charge transfer processes, resulting in slow reaction kinetics that severely hinder hydrogen production efficiency during water splitting. Therefore, there is an urgent need to explore low-cost, highly active, and highly stable bifunctional catalysts to achieve efficient H2 production.
[0003] Among various non-noble metal catalysts, nickel sulfides, such as NiS and Ni3S2, have attracted widespread attention due to their low cost, ease of preparation, good conductivity, and unique structure. However, the electrocatalytic activity and long-term stability of nickel sulfides under electrolysis conditions still need further improvement to meet the demands of practical applications.
[0004] Therefore, it is necessary to develop water electrolysis catalysts with high activity and stability, which will help realize future sustainable energy and large-scale industrial hydrogen production. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the morphology and size of catalyst materials can be controlled by doping with heteroatoms. This also allows for the adjustment of the electronic structure of the catalyst, which helps to increase the exposure of active sites, effectively promotes the transport and diffusion of electrolyte ions, and enables the material to exhibit good catalytic activity, thereby accelerating reaction kinetics.
[0006] In one aspect, the present invention provides a method for preparing a composite material with a coated V-doped Ni3S2 core-shell structure, the method comprising the following steps: Step (1): Dissolve nickel nitrate, vanadium chloride, and urea in a mixed solvent of methanol and ultrapure water, sonicate to form a homogeneous solution, then transfer the solution and nickel foam to a polytetrafluoroethylene liner, place it in a stainless steel autoclave, carry out a hydrothermal reaction, and after cooling to room temperature, wash it several times with ultrapure water and dry it to obtain NiV-LDH. Step (2): Thiourea is dissolved in water to form a homogeneous solution, and together with the product NiV-LDH obtained in step (1), it is transferred to a polytetrafluoroethylene liner and placed in a stainless steel autoclave for hydrothermal reaction. After cooling to room temperature, it is washed several times with ultrapure water and dried to obtain V-doped Ni3S2. Step (3): Add nickel salt to ultrapure water and sonicate to obtain a mixed solution as an electrolyte solution. Electrodeposition is performed directly by electrochemical method to obtain the coated V-doped Ni3S2 three-dimensional core-shell structure material.
[0007] The NiV-LDH obtained in step (1) has a hydrotalcite structure.
[0008] Further, in step (1), the mass ratio of nickel nitrate, vanadium chloride and urea is 10-8:0.1-1:1-6, preferably 4.7:0.3:3.6.
[0009] Furthermore, in step (1), the volume ratio of methanol to ultrapure water is 1:6-6:1, preferably 1:2.
[0010] Furthermore, step (1) also includes pretreatment of the nickel foam: the nickel foam is cleaned sequentially with 2~5 mol / L hydrochloric acid, deionized water, acetone and ethanol-water solution, and finally dried in an oven at 20~60℃, preferably 40℃, for 2~4 hours.
[0011] Furthermore, in step (1), the hydrothermal reaction temperature is 100-130℃, preferably 120℃; the hydrothermal reaction time is 4-10 h, preferably 6 h.
[0012] Furthermore, in step (2), the hydrothermal reaction temperature is 135-180℃, preferably 160℃; the hydrothermal reaction time is 4-10 h, preferably 6 h.
[0013] Further, in step (3), the nickel salt is nickel nitrate and / or nickel acetate, and the concentration of nickel in the electrolyte is 0.01 mol / L to 0.1 mol / L, preferably 0.05 mol / L.
[0014] Further, in step (3), the electrochemical method is cyclic voltammetry, with a voltage range of -3 V ~ 3 V / SCE, preferably -1.1 V ~ 0 V / SCE; a scan rate of 0 mV / s ~ 100 mV / s, preferably 50 mV / s; and a scan number of cycles of 0 ~ 100, preferably 30.
[0015] Further, in step (3), the working electrode of the cyclic voltammetry is the self-supporting electrode of the V-doped Ni3S2; the counter electrode is a platinum electrode; and the reference electrode is a saturated calomel electrode (SCE).
[0016] In another aspect, the present invention provides a composite material with a coated V-doped Ni3S2 core-shell structure prepared by the above method.
[0017] Furthermore, the XRD diffraction peaks of the composite material at 22.25°, 31.6°, 38.3°, 50.1°, and 55.55° coincide with the (101), (110), (003), (113), and (122) crystal planes of Ni3S2 (JCPDS No. 44-1418) and there are no other impurity peaks, indicating that the generated phase is the Ni3S2 phase.
[0018] In another aspect, the present invention provides the application of the coated V-doped Ni3S2 core-shell structure composite material in the water electrolysis reaction.
[0019] Furthermore, in the OER performance test conducted by the linear sweep voltammetry method, the lowest overpotential of the composite material was 116 mV.
[0020] Furthermore, in the HER performance test conducted by linear sweep voltammetry, the lowest overpotential of the composite material was 174 mV.
[0021] Beneficial effects The preparation method of the present invention uses nickel foam as a substrate. The direct growth of Ni3S2 on nickel foam improves the charge transport efficiency between the catalyst and the substrate and the stability of the catalytic material. In addition, by doping V into the Ni3S2 material, the morphology and electronic structure of Ni3S2 are successfully controlled.
[0022] The preparation method of the present invention enables V to be uniformly doped into the material, V 4+ It has a strong affinity for oxygen atoms, and during electrocatalysis, leaching in an alkaline electrolyte facilitates the exposure of more sites on the catalyst surface, leading to the formation of abundant Ni in the catalyst. 3+ This further improves the overall efficiency of water electrolysis.
[0023] The preparation method of the present invention enables successful deposition of nanosheets in the electrodeposition step, which further increases the exposure of active sites in the material, provides a large surface area and a large number of open channels, and promotes the adsorption of reactants, close contact with electrolytes and rapid release of gaseous products.
[0024] The preparation method of this invention introduces V element into Ni3S2, which can further improve its conductivity and catalytic activity. Using V-doped Ni3S2 nanorod arrays as a good conductive substrate, and combining them with ultrathin nanosheets, a three-dimensional core-shell structured catalytic material is formed to achieve better catalytic performance.
[0025] The preparation method of the present invention can effectively prepare composite catalytic materials with coated V-doped Ni3S2 core-shell structure, which have excellent electrochemical hydrogen evolution and oxygen evolution performance and long-term stability. Attached Figure Description
[0026] Figure 1 The X-ray diffraction patterns of the samples prepared in Examples 1-3 and Comparative Examples 1-2 are shown. Figure 2 Scanning electron microscope image of the V-doped Ni3S2 three-dimensional core-shell structure self-supporting electrode prepared in Example 2; Figure 3 Transmission electron microscope image of the V-doped Ni3S2 three-dimensional core-shell structure self-supporting electrode prepared in Example 2; Figure 4 The elemental distribution of the coated V-doped Ni3S2 three-dimensional core-shell structure self-supporting electrode prepared in Example 2; Figure 5 The OER performance graphs are for the samples prepared in Examples 1-3 and Comparative Examples 1-2. Figure 6 The HER performance graphs are for the samples prepared in Examples 1-3 and Comparative Examples 1-2. Figure 7 The OER stability diagram of the coated V-doped Ni3S2 three-dimensional core-shell structure self-supporting electrode prepared in Example 2; Figure 8 The HER stability diagram of the V-doped Ni3S2 three-dimensional core-shell structure self-supporting electrode prepared in Example 2 is shown. Figure 9 Tafel plots of OER for the samples prepared in Examples 1-3 and Comparative Examples 1-2; Figure 10 Tafel plots of HER for the samples prepared in Examples 1-3 and Comparative Examples 1-2.
[0027] Specific implementation methods The technical solution of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings; unless otherwise specified, all reagents used in the present invention can be obtained by purchase.
[0028] The nickel foam used in the following examples was pretreated by sequentially cleaning it with 3 mol / L hydrochloric acid, deionized water, acetone, and ethanol-water solution, and finally drying it in an oven at 40°C for 3 h.
[0029] Example 1 Step (1): Dissolve 0.47 g nickel nitrate, 0.03 g vanadium chloride, and 0.36 g urea in a mixed solvent of 10 ml methanol and 20 ml water, and sonicate to form a homogeneous solution. Then, transfer the above solution and two pretreated nickel foam sheets to a polytetrafluoroethylene liner, place them in a stainless steel autoclave, and hydrothermally react at 120°C for 6 hours. After cooling to room temperature, wash several times with ultrapure water and dry to obtain NiV-LDH.
[0030] Step (2): Dissolve 0.57 g of thiourea in 30 ml of water to form a homogeneous solution. Transfer the solution together with the product NiV-LDH obtained in step (1) to a polytetrafluoroethylene liner and place it in a stainless steel autoclave. Perform hydrothermal reaction at 160 °C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain V-doped Ni3S2.
[0031] Step (3) Electrodeposition: A three-electrode system was used to scan 10 times at a rate of 50 mV / s within a scanning range of -1.1 V to 0 V / SCE to obtain a composite catalytic material with a three-dimensional core-shell structure of V-doped Ni3S2. After the electrodeposition process, the product was washed and dried with distilled water. The platinum electrode was used as the counter electrode, the saturated calomel electrode was used as the reference electrode, the V-doped Ni3S2 electrode obtained in step (2) was used as the working electrode, and the electrolyte was 50 ml of a mixed solution of 0.018 mol / L nickel nitrate and 0.032 mmol / L nickel acetate.
[0032] Example 2 Step (1): Dissolve 0.47 g nickel nitrate, 0.03 g vanadium chloride, and 0.36 g urea in a mixed solvent of 10 ml methanol and 20 ml water, and sonicate to form a homogeneous solution. Then, transfer the above solution and two pretreated nickel foam sheets to a polytetrafluoroethylene liner, place them in a stainless steel autoclave, and hydrothermally react at 120°C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain NiV-LDH.
[0033] Step (2): Dissolve 0.57 g of thiourea in 30 ml of water to form a homogeneous solution. Transfer the solution together with the product NiV-LDH obtained in step (1) to a polytetrafluoroethylene liner and place it in a stainless steel autoclave. Perform hydrothermal reaction at 160 °C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain V-doped Ni3S2.
[0034] Step (3) Electrodeposition: A three-electrode system was used to scan 30 times at a rate of 50 mV / s within a scanning range of -1.1 V to 0 V / SCE to obtain a composite catalytic material with a three-dimensional core-shell structure of V-doped Ni3S2. After the electrodeposition process, the product was washed and dried with distilled water. The platinum electrode was used as the counter electrode, the saturated calomel electrode was used as the reference electrode, the V-doped Ni3S2 electrode obtained in step (2) was used as the working electrode, and the electrolyte was 50 ml of a mixed solution of 0.018 mol / L nickel nitrate and 0.032 mmol / L nickel acetate.
[0035] Example 3: Step (1): Dissolve 0.47 g nickel nitrate, 0.03 g vanadium chloride, and 0.36 g urea in a mixed solvent of 10 ml methanol and 20 ml water, and sonicate to form a homogeneous solution. Then, transfer the above solution and two pretreated nickel foam sheets to a polytetrafluoroethylene liner, place them in a stainless steel autoclave, and hydrothermally react at 120°C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain NiV-LDH.
[0036] Step (2): Dissolve 0.57 g of thiourea in 30 ml of water to form a homogeneous solution. Transfer the solution together with the product NiV-LDH obtained in step (1) to a polytetrafluoroethylene liner and place it in a stainless steel autoclave. Perform hydrothermal reaction at 160 °C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain V-doped Ni3S2.
[0037] Step (3) Electrodeposition: A three-electrode system was used to scan 50 times at a rate of 50 mV / s within a scanning range of -1.1 V to 0 V / SCE to obtain a composite catalytic material with a three-dimensional core-shell structure of V-doped Ni3S2. After the electrodeposition process, the product was washed and dried with distilled water. The platinum electrode was used as the counter electrode, the saturated calomel electrode as the reference electrode, and the V-doped Ni3S2 electrode obtained in step (2) as the working electrode. The electrolyte was 50 ml of a mixed solution of 0.018 mol / L nickel nitrate and 0.032 mmol / L nickel acetate.
[0038] Comparative Example 1: Step (1): Dissolve 0.47 g of nickel nitrate and 0.3 g of urea in a mixed solvent of 10 ml of methanol and 20 ml of water, and sonicate to form a homogeneous solution. Then, transfer the above solution and two pretreated nickel foam sheets to a polytetrafluoroethylene liner, place them in a stainless steel autoclave, and hydrothermally react at 120°C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain Ni-LDH.
[0039] Step (2): Dissolve 0.57 g of thiourea in 30 ml of water to form a homogeneous solution. Transfer the solution together with the product NiV-LDH obtained in step (1) to a polytetrafluoroethylene liner and place it in a stainless steel autoclave. Perform hydrothermal reaction at 160 °C for 6 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain Ni3S2.
[0040] Comparative Example 2: Step (1): Dissolve 0.47 g nickel nitrate, 0.03 g vanadium chloride, and 0.36 g urea in a mixed solvent of 10 ml methanol and 20 ml water, and sonicate to form a homogeneous solution. Then, transfer the above solution and two pretreated nickel foam sheets to a polytetrafluoroethylene liner, place them in a stainless steel autoclave, and hydrothermally react at 120°C for 8 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain NiV-LDH.
[0041] Step (2): Dissolve 0.57 g of thiourea in 30 ml of water to form a homogeneous solution. Transfer the solution together with the product NiV-LDH obtained in step (1) to a polytetrafluoroethylene liner and place it in a stainless steel autoclave. Perform hydrothermal reaction at 150 °C for 8 h. After cooling to room temperature, wash several times with ultrapure water and dry to obtain V-doped Ni3S2.
[0042] The X-ray diffraction patterns of the samples prepared in Examples 1-3 and Comparative Examples 1-2 are as follows: Figure 1 As shown, it can be seen that the XRD diffraction peaks of the samples in Examples 1-3 and Comparative Examples 1-2 at 22.25°, 31.6°, 38.3°, 50.1°, and 55.55° are consistent with the (101)(110)(003)(113)(122) crystal planes of Ni3S2 (JCPDS No. 44-1418) and there are no other impurity peaks, indicating that the generated phase is Ni3S2 phase.
[0043] Scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, and elemental distributions of the coated V-doped Ni3S2 three-dimensional core-shell structure self-supporting electrode prepared in Example 2 are shown below. Figures 2-4 As shown.
[0044] like Figure 2 As shown in the scanning electron microscope image of the sample prepared in Example 2, many nanosheets grow uniformly and vertically on the nanorods, forming a unique three-dimensional core-shell nanostructure.
[0045] like Figure 3 As shown, the transmission electron microscope image of the sample prepared in Example 2 further reveals the core-shell nanostructure of V-doped Ni3S2 nanorod core and nanosheet outer layer, with the nanosheets interconnected.
[0046] like Figure 4As shown in the image, the elemental mapping of the sample prepared in Example 2 shows that S, Ni, and V are uniformly distributed in the composite material, confirming the presence of V and the successful assembly of the nanorod structure on nickel foam.
[0047] Electrochemical performance of Examples 1-3 and Comparative Examples 1-2 was tested using an electrochemical workstation with a three-electrode system. The working electrode was the self-supporting electrode prepared in Examples 1-3 and Comparative Examples 1-2 of this invention; the reference electrode was a Hg / HgO electrode (standard potential of +0.9122 V (25℃)); and the counter electrode was a carbon rod electrode. OER performance was tested using linear sweep voltammetry, with a scan range of 0 V to 1.4 V and a scan rate of 5 mV / s. HER performance was tested using linear sweep voltammetry, with a scan range of -0.9 V to -1.8 V and a scan rate of 5 mV / s. The results are as follows: Figures 5-10 As shown.
[0048] like Figure 5 The OER performance graphs for the samples prepared in Examples 1-3 and Comparative Examples 1-2 are obtained by linear sweep voltammetry. The sample in Example 2 has the lowest overpotential of 116 mV (current density of 10 mA / cm²) among the five samples. 2 ).
[0049] like Figure 6 The graphs show the HER performance of the samples prepared in Examples 1-3 and Comparative Examples 1-2, measured by linear sweep voltammetry. The sample in Example 2 exhibits the lowest overpotential of 174 mV (current density of 10 mA / cm²) among these five samples. 2 ).
[0050] like Figure 7 It can be seen that the sample prepared in Example 2, when tested with an OER current density of 10 mA / cm², showed good performance. 2 It can maintain stability for at least 96 hours without significant degradation, indicating that the sample has good OER stability.
[0051] like Figure 8 It can be seen that the sample prepared in Example 2, when tested with a current density of 10 mA / cm², showed good performance. 2 It can maintain stability for at least 96 hours without significant degradation, indicating that the sample has good HER stability.
[0052] like Figure 9 The samples prepared for Example 2 and Comparative Examples 1-2 showed the smallest Tafel slope during OER testing, at 62.09 mV / dec, indicating that these samples possessed relatively fast OER catalytic kinetics.
[0053] like Figure 10 The samples prepared for Example 2 and Comparative Examples 1-2 showed the smallest Tafel slope of 178.22 mV / dec during HER testing, indicating that these samples possessed relatively fast HER catalytic kinetics.
[0054] In summary, this invention successfully deposits nanosheets on V-doped Ni3S2 nanorods to form a three-dimensional core-shell composite nanomaterial, providing a large number of active sites, promoting electrolyte diffusion and bubble release, while also possessing high catalytic activity and stability for water electrolysis.
[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.
Claims
1. The application of a coated V-doped Ni3S2 core-shell composite material in water electrolysis, wherein the preparation method of the coated V-doped Ni3S2 core-shell composite material includes the following steps: Step (1): Dissolve nickel nitrate, vanadium chloride, and urea in a mixed solvent of methanol and ultrapure water, sonicate to form a homogeneous solution, then transfer the solution and nickel foam to a polytetrafluoroethylene liner, place it in a stainless steel autoclave, carry out a hydrothermal reaction, and after cooling to room temperature, wash with ultrapure water and dry to obtain NiV-LDH. Step (2): Thiourea is dissolved in water to form a homogeneous solution, and together with the product NiV-LDH obtained in step (1), it is transferred to a polytetrafluoroethylene liner and placed in a stainless steel autoclave for hydrothermal reaction. After cooling to room temperature, it is washed with ultrapure water and dried to obtain V-doped Ni3S2. Step (3): Add nickel salt to ultrapure water and sonicate to obtain a mixed solution as an electrolyte solution. Electrodeposition is performed directly by electrochemical method to obtain a composite material with a V-doped Ni3S2 core-shell structure. In step (3), the nickel salt is nickel nitrate, and the electrolyte solution concentration is 0.01 mol / L to 0.1 mol / L; the electrochemical method is cyclic voltammetry, with a voltage range of -3 V to 3 V / SCE; a scan rate of 0 mV / s to 100 mV / s; and a scan cycle count of 0 to 100 cycles; the working electrode of the cyclic voltammetry is the self-supporting electrode of the V-doped Ni3S2; the counter electrode is a platinum electrode; and the reference electrode is a saturated calomel electrode (SCE). In the composite material with the coated V-doped Ni3S2 core-shell structure, nanosheets grow uniformly and vertically on the nanorods, forming a unique three-dimensional core-shell nanostructure. In the OER performance test using the linear sweep voltammetry method, the lowest overpotential of the composite material was 116 mV at a current density of 10 mA / cm². 2 It can maintain stability for at least 96 hours; In the HER performance test using linear sweep voltammetry, the lowest overpotential of the composite material was 174 mV at a current density of 10 mA / cm². 2 It can maintain stability for at least 96 hours.
2. The application according to claim 1, characterized in that, In step (1), the mass ratio of nickel nitrate, vanadium chloride, and urea is 10⁻⁸: 0.1-1：1-6。 3. The application according to claim 1, characterized in that, Step (1) also includes pretreatment of the nickel foam: the nickel foam is cleaned sequentially with 2~5 mol / L hydrochloric acid, deionized water, acetone and ethanol-water solution, and finally dried in an oven at 20~60℃ for 2~4 h.
4. The application according to claim 1, characterized in that, In step (1), the hydrothermal reaction temperature is 100-130℃; the hydrothermal reaction time is 4-10 h.
5. The application according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 135-180℃; the hydrothermal reaction time is 4-10 h.
6. The application according to claim 1, characterized in that, In step (3), the concentration of the electrolyte is 0.05 mol / L.
7. The application according to claim 1, characterized in that, In step (3), the electrochemical method is cyclic voltammetry, with a voltage range of -1.1V to 0V / SCE; a scan rate of 50 mV / s; and a scan cycle of 30 cycles.