Electrode materials with core-shell structure, electrode composite layers and their applications

Abstract

This application discloses an electrode material, an electrode composite layer, and its applications having a core-shell structure. The core region of the electrode material comprises a metal-doped nickel sulfide, and the shell region comprises a nickel-containing compound. The shell structure employed in this application protects the chemical stability of the metal-doped nickel sulfide material while retaining its high electronic conductivity. The resulting heterogeneous structure provides more active sites for the catalytic layer on the electrode surface, ultimately resulting in higher electrochemical activity and stability for the electrode material as a whole.

Description

Technical Field

[0001] The present application relates to the field of electrode technology, and in particular to an electrode material with a core-shell structure, an electrode composite layer, and applications thereof. Background Art

[0002] The mission of reforming the energy structure forces researchers to focus their current attention on the exploration of a new generation of clean and sustainable energy. Currently, hydrogen energy has received widespread attention as a green, safe and sustainable energy source. High-purity hydrogen can be produced by catalytic electrolysis of water. The water decomposition reaction is divided into two half-reactions: oxygen evolution reaction and hydrogen evolution reaction, involving multiple steps of electron transfer and material transfer processes, and has a high power consumption. Suitable electrocatalysts can greatly improve the efficiency of electrocatalytic water splitting and reduce the power consumption required for water decomposition. As the core component of the electrolytic cell, the cost and efficiency of the electrocatalyst will also greatly affect the economic efficiency of the produced hydrogen.

[0003] Currently, precious metal platinum-, Ir-, and Ru-based materials are still recognized as benchmark catalysts for hydrogen and oxygen evolution reactions, demonstrating excellent catalytic activity for both reactions. However, these precious metal materials are limited in reserves and expensive, making their use in large-scale hydrogen production difficult. Therefore, the design and synthesis of cost-effective, highly active, and stable non-precious metal-based electrocatalyst materials has become an urgent task in the development of the hydrogen economy in recent years.

[0004] Nickel-based transition metal compounds, such as nickel sulfide and nickel nitride, are widely used in electrocatalysis research due to their low cost, controllable synthesis, and high intrinsic electrocatalytic activity. Doping with metal elements such as vanadium, iron, molybdenum, cobalt, and tin can effectively regulate the morphology and binding energy of hydrogen adsorption intermediates of nickel-based catalysts such as nickel sulfide, thereby exhibiting enhanced electrocatalytic activity. However, research has found that during the alkaline oxygen evolution process, these surface doped metals gradually precipitate due to direct contact with the alkaline solution, ultimately causing changes or even collapse in the material's microstructure, which significantly affects the long-term stability of such electrode materials. Summary of the Invention

[0005] In order to solve the stability problem of metal-doped nickel sulfide in the prior art, the present application provides an electrode material, an electrode composite layer and its application with a core-shell structure. The electrode material has high structural stability due to the protection of the core layer by the shell structure. At the same time, due to the realization of multiple interface sites, the electrode material has high electrocatalytic and electrochemical activity.

[0006] In addition, the core-shell structure electrode material proposed in this application has a metal-doped nickel sulfide core and a nickel compound as a shell. This structure can significantly improve the stability of the metal-doped nickel sulfide electrode material. At the same time, the electrode has multiple interfacial active sites, which makes it have higher electrocatalytic and electrochemical activity than a single-component nickel-based compound electrode material.

[0007] The specific technical solutions of this application are as follows:

[0008] 1. An electrode material having a core-shell structure, wherein the core region of the material comprises a metal-doped nickel sulfide and the shell region comprises a nickel-containing compound.

[0009] 2. The electrode material according to item 1, wherein the metal of the metal-doped nickel sulfide is one or more of vanadium, molybdenum, iron, cobalt, and tin.

[0010] 3. The electrode material according to item 1, wherein the nickel-containing compound comprises one of nickel nitride, nickel carbide, nickel sulfide or nickel phosphide.

[0011] 4. The electrode material according to item 1, wherein the shell region of the material further contains other metal elements for doping, and the other metal elements are selected from one or more of molybdenum, vanadium, iron, cobalt, copper, tungsten and ruthenium.

[0012] 5. The electrode material according to item 1, wherein the molar content of the doping metal in the metal-doped nickel sulfide gradually decreases from the center of the material to the outside, and preferably, the molar content of the doping metal near the shell region is less than 10%, preferably less than 7%;

[0013] Preferably, the molar content of the doping metal near the central region of the material is 5-40%, preferably 8-30%, and more preferably 10-25%.

[0014] 6. The electrode material according to any one of items 1 to 5, wherein the shell region has open pores with an average porosity of 20-70%, preferably 30-65%, and more preferably 35-60%.

[0015] 7. The electrode material according to any one of items 1 to 3, wherein the core region comprises vanadium-nickel sulfide, elemental nickel, and nickel oxide;

[0016] The vanadium-nickel sulfide comprises Ni3S2, unsaturated vanadium sulfide and NiS;

[0017] Preferably, the Ni3S2 is 10-70% by mass in the vanadium-nickel sulfide, preferably 20-60%, and more preferably 25-50%;

[0018] The unsaturated vanadium sulfide is 1-30%, preferably 2-20%, and more preferably 3-10%.

[0019] 8. The electrode material according to any one of items 1 to 3, wherein the shell region comprises nickel nitride, nickel oxide and vanadium nitride, and the nickel nitride comprises nickel nitride and / or unsaturated nitrided nickel.

[0020] 9. The electrode material according to any one of item 8, wherein the nitrogen molar content in the shell region gradually decreases from the shell region to the core region;

[0021] Preferably, the molar nitrogen content of the shell region adjacent to the core region is less than 10%, preferably less than 5%.

[0022] 10. The electrode material according to any one of items 1 to 3, wherein the electrode material has the morphology of nanorods, nanosheets or nanospheres.

[0023] 11. The electrode material according to item 10, wherein the thickness of the core region accounts for 60-99%, preferably 70-98%, and more preferably 80-95% of the thickness of the longitudinal section of the electrode material.

[0024] 12. The electrode material according to item 10, wherein the thickness of the shell region accounts for 0.01-40%, preferably 0.01-30%, and more preferably 0.5-20% of the width of the longitudinal section of the electrolytic material.

[0025] 13. A method for preparing an electrode material, comprising:

[0026] In-situ growth of metal-doped nickel-containing sulfide on the surface of the nickel-containing material;

[0027] treating the surface layer to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer;

[0028] The surface layer of the metal-doped nickel-containing sulfide coated with the nickel oxide layer is treated to obtain an electrode material in which the shell region comprises the nickel-containing compound and the core region comprises the metal-doped nickel sulfide.

[0029] 14. The method according to claim 13, wherein the method of in-situ growing metal-doped nickel-containing sulfide on the surface of the nickel-containing material comprises:

[0030] mixing a doping metal source and a sulfur source and dissolving them in a solvent to obtain a precursor solution;

[0031] The precursor solution is mixed with the nickel-containing material for reaction.

[0032] 15. The method according to item 13, wherein the doping metal source is one or more of a vanadium source, an iron source, a molybdenum source, a cobalt source or a tin source.

[0033] 16. The method according to item 15, wherein the doping metal source is a vanadium source, and the vanadium source is vanadium powder, vanadium chloride, sodium vanadate, sodium metavanadate, vanadium pentoxide or sodium vanadate dodecahydrate; preferably, the concentration of the vanadium source is 1-80 mM, preferably 2-60 mM, and further preferably 3-40 mM.

[0034] 17. The method according to item 14, wherein in the precursor solution, the molar ratio of the metal source in the doping metal source to the sulfur in the sulfur source is 1:0.1-30, preferably 1:0.3-25, and more preferably 1:0.5-20;

[0035] Preferably, the sulfur source is an inorganic sulfur source or an organic sulfur source. Preferably, the inorganic sulfur source is sulfur dioxide or sodium dithionite; the organic sulfur source is thiourea or thioacetamide;

[0036] Preferably, the solvent is water, ethanol, ethylene glycol or glycerol.

[0037] 18. The method of claim 14, wherein the mixing of the precursor solution and the nickel-containing material comprises:

[0038] The precursor solution and the nickel-containing material are placed in a hydrothermal reactor for mixing and reacting, preferably performing a hydrothermal or solvothermal reaction.

[0039] 19. The method according to item 18, wherein the reaction is carried out at 90-200°C, preferably at 100-180°C, and preferably, the reaction time is 0.2-30h, preferably 1-10h.

[0040] 20. The method according to item 13, wherein treating the surface layer to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer comprises: electrochemically oxidizing the nickel-containing material having a surface layer containing a metal-doped nickel-containing sulfide to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer, preferably, the deposition voltage of the electrochemical oxidation is 0.2-1.4 V, preferably 0.5-1.3 V, and more preferably 0.6-1.25 V;

[0041] Preferably, the deposition time of electrochemical oxidation is 0.1-60 min, preferably 0.3-30 min, and more preferably 0.4-10 min.

[0042] 21. The method according to claim 13, wherein the method of treating the surface layer of the metal-doped nickel-containing sulfide coated with the nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide comprises:

[0043] calcining the metal-doped nickel-containing sulfide coated with the nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide, preferably at a calcination temperature of 200-600° C., preferably 250-400° C., and more preferably 300-400° C.;

[0044] Preferably, the calcination time is 0.5-25 h, preferably 1-10 h, and more preferably 2-5 h.

[0045] 22. The method according to item 13, wherein the nickel-containing material is a nickel substrate or particles containing a nickel element. Preferably, when the nickel-containing material is a nickel substrate, the surface of the nickel substrate needs to be cleaned.

[0046] 23. The method according to item 13, wherein the electrode material is the electrode material according to any one of claims 1 to 12.

[0047] 24. An electrode composite layer comprising a nickel base layer and the electrode material described in any one of items 1 to 12 or the electrode material prepared by the method described in any one of items 13 to 23, wherein the electrode material is disposed on the nickel base layer.

[0048] 25. The array electrode according to item 24, wherein the thickness of the nickel base layer accounts for 20-90% of the thickness of the electrode material, preferably 30-85%, and more preferably 40-70%;

[0049] Preferably, the porosity of the nickel base layer is less than 5%, preferably less than 2%;

[0050] Preferably, the diameter of the nickel base layer is 100-500 μm, preferably 200-300 μm;

[0051] Preferably, the pore size of the nickel base layer is 0.02-2.0 mm, preferably 0.2-1 mm.

[0052] 26. Use of the electrode composite layer described in item 24 or 25 in the field of catalysis.

[0053] 27. The use according to item 26, wherein the catalytic field is electrocatalytic decomposition of water or electrocatalytic reduction of carbon dioxide.

[0054] 28. Use of the electrode composite layer described in item 24 or 25 in the field of electrochemistry.

[0055] Effects of the Invention

[0056] This application uses a shell structure to protect the chemical stability of the metal-doped nickel sulfide material while retaining its high electronic conductivity. The heterogeneous structure formed can provide more active sites for the catalytic layer on the electrode surface, ultimately making the electrode material as a whole exhibit higher electrochemical activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the rod-shaped electrode material obtained in the present application, wherein a is a three-dimensional schematic diagram and b is a central longitudinal section schematic diagram.

[0058] Figure 2 Schematic diagram of the cross section of the array electrode formed by the rod-shaped electrode material obtained in the present application, wherein a is a schematic diagram of the central transverse and longitudinal sections, and b is a schematic diagram of the cross section.

[0059] Figure 3 This is a flow chart of the preparation of array electrodes in this application.

[0060] Among them, 1-core region, 2-shell region, 3-nickel base layer, 4-array layer formed by nanorods, L1-thickness of core layer, L-thickness of base DETAILED DESCRIPTION

[0061] The present application is described in detail below with reference to the embodiments described in the accompanying drawings, wherein like numbers in all figures represent like features. Although specific embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0062] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" are open-ended terms and should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present application, but the description is based on the general principles of the specification and is not intended to limit the scope of the present application. The scope of protection of this application shall be as defined by the attached claims.

[0063] The present application provides an electrode material with a core-shell structure, wherein the core region of the material comprises metal-doped nickel sulfide, and the shell region comprises a nickel-containing compound.

[0064] The core region contains metal-doped nickel sulfide, which can maintain the overall structure of the material and has good electronic conductivity, providing a fast electron transmission channel for electrocatalysis or electrochemical reactions; and providing a guarantee for the overall material to achieve higher electrocatalysis or electrochemical reaction efficiency.

[0065] The shell region contains a nickel-containing compound, which serves as the main catalytically active layer in the electrode and has multiple catalytically active centers. Its surface layer has abundant open pores, which can increase the catalytic reaction area. The nickel-containing compound obtained by in-situ conversion of surface nickel oxide has a structure that can stably contact the core region interface, ensuring the overall structural stability of the electrode.

[0066] In some embodiments, the metal of the metal-doped nickel sulfide is one or more of vanadium, molybdenum, iron, cobalt, and tin. In some embodiments, the nickel-containing compound comprises one of nickel nitride, nickel carbide, nickel sulfide, or nickel phosphide. In some embodiments, the shell region of the material further comprises other metal elements for doping, and the other metal elements are selected from one or more of molybdenum, vanadium, iron, cobalt, copper, tungsten, and ruthenium.

[0067] In some embodiments, the molar content of the doping metal in the metal-doped nickel sulfide gradually decreases from the center of the material to the outside, preferably, the molar content of the doping metal near the shell region is less than 10%, preferably less than 7%;

[0068] Preferably, the molar content of the doping metal near the central region of the material is 5-40%, preferably 8-30%, and more preferably 10-25%.

[0069] In the present application, there is no limitation on the method for determining the molar content of the doping metal in the metal-doped nickel sulfide. It can be determined according to conventional methods. For example, the molar content of the doping metal element can be analyzed using X-ray energy dispersive spectroscopy (EDS) or X-ray photoelectron spectroscopy (XPS). Preferably, a transmission electron microscope (TEM) is used to photograph the material to obtain EDS, and the EDS is analyzed to obtain the molar content of the doping metal element.

[0070] In the present application, the distribution state and content of the doped metal elements at different depth layers can be analyzed by combining the above analysis method with ion etching.

[0071] For example, the molar content of the doping metal in the region near the shell region may be 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, etc.;

[0072] The molar content of the doping metal near the center region of the material may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0073] The present application limits the molar content of the doped metal in the core region to the above-mentioned range, which is of great significance for maintaining the high reactivity and high conductivity of nickel sulfide. The lower molar content of the doped metal near the shell region ensures the overall stability of the material, and the higher doped metal content near the center region of the material can regulate the characteristic morphology of nickel sulfide and maintain high conductivity.

[0074] In some embodiments, the shell region has open pores with an average porosity of 20-70%, preferably 30-65%, and more preferably 35-60%.

[0075] In the present application, the shell region has abundant open pores, which are residual pores caused by the partial precipitation and dissolution of doped metal elements into the electrolyte during the electrochemical pre-oxidation process of the nickel-containing compound.

[0076] In the present application, there is no limitation on the shape of the hole, which can be any shape.

[0077] In the present application, the average opening size of the pores is 2-500 nm, preferably 5-300 nm.

[0078] For example, the average opening size of the pores is 2 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc.

[0079] In the present application, there is no limitation on the method for measuring porosity, and the porosity may be measured using conventional methods in the art, such as gas adsorption method and mercury intrusion method.

[0080] In the present application, the opening size of the pores can be determined by measuring the SEM images.

[0081] For example, the average porosity can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.

[0082] In some embodiments, the core region comprises vanadium-nickel sulfide, elemental nickel, and nickel oxide;

[0083] The vanadium-nickel sulfide comprises Ni3S2, unsaturated vanadium sulfide and NiS;

[0084] Preferably, the Ni3S2 is 10-70% by mass in the vanadium-nickel sulfide, preferably 20-60%, and more preferably 25-50%;

[0085] The unsaturated vanadium sulfide is 1-30%, preferably 2-20%, and more preferably 3-10%.

[0086] For example, in terms of mass percentage in vanadium-nickel sulfide, the Ni3S2 can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, etc.;

[0087] The unsaturated vanadium sulfide may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc.

[0088] In the present application, for the determination of the content of Ni3S2, unsaturated vanadium sulfide and NiS, the diffraction peak information of the above substances can be obtained by X-ray diffraction, and then the type of substance is determined by high-resolution transmission electron microscopy, and then the content of the substance is determined. Preferably, the content of the above substances is determined by the following method:

[0089] The diffraction peak information of the above substances can be obtained by X-ray diffraction (XRD), which may be a composite diffraction peak of the above substances. Then, the lattice fringes of different components in the obtained sample can be observed by high-resolution transmission electron microscopy (HR-TEM) of the material to determine the type of substance. Then, the bond type and corresponding content of the corresponding elements are analyzed by elemental energy spectrum, Raman spectrum and X-ray photoelectron spectroscopy (XPS). Among them, the peak at 164-165eV in the XPS region of S (calibrated by the C1s peak of 284.8eV) is attributed to the bridging sulfur ion (S2 2- ), which is an unsaturated sulfur edge site.

[0090] In some embodiments, the unsaturated vanadium sulfide is rich in unsaturated S sites.

[0091] In some embodiments, the shell region comprises nickel nitride, nickel oxide, and vanadium nitride, wherein the nickel nitride comprises nickel nitride and / or unsaturated nitrided nickel. In some embodiments, the nitrogen molar content in the shell region gradually decreases from the shell region to the core region;

[0092] Preferably, the molar nitrogen content of the shell region adjacent to the core region is less than 10%, preferably less than 5%.

[0093] In the present application, there is no limitation on the method for determining the nitrogen content, and the nitrogen content may be measured using conventional methods in the art, for example, by X-ray energy spectrum scanning.

[0094] In the present application, for the determination of the substances in the nickel nitride layer, X-ray diffraction (XRD) can be used to obtain the diffraction peak information of the crystalline material therein, and high-resolution transmission electron microscopy (HR-TEM) can be used to observe the lattice stripes and obvious lattice distortion of different substances to determine the type of substance, and the bonding formation of Ni is analyzed by X-ray photoelectron spectroscopy to determine the above-mentioned substances. Preferably, the diffraction peak information of the crystalline material therein can be obtained by XRD, which may be a composite diffraction peak of several substances. Then, HR-TEM can be used to observe the lattice stripes and obvious lattice distortion of different components in the obtained sample to determine the type of substance, and then X-ray photoelectron spectroscopy can be used to analyze the bonding form of Ni and thus determine the above-mentioned substances.

[0095] For example, the molar nitrogen content of the shell region near the core region can be 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, etc.

[0096] In some embodiments, the electrode material has the morphology of nanorods, nanosheets, or nanospheres.

[0097] Figure 1 is a schematic diagram of an electrode material in a specific embodiment of the present application, such as Figure 1 As shown, it is an electrode material in the shape of a nanorod, wherein a is a three-dimensional schematic diagram of the core-shell structure material, b is a central cross-sectional schematic diagram of the core-shell structure material, 1 is the core region, 2 is the shell region, and the interface between the core region and the shell region can be a regular shape or an irregular shape.

[0098] The nanosheet refers to a structure with a thickness of 1-100nm and a lateral size of 50nm-20μm. The nanosheet with a core-shell structure refers to a nanosheet with a core region and a layer of material wrapped on the surface of the nanosheet as a shell region.

[0099] The nanosphere refers to a zero-dimensional or near-zero-dimensional structure with a diameter of 20-500 nm. In this application, a nanosphere with a core-shell structure refers to a nanosphere with a core region and a layer wrapped on the surface of the nanosphere as a shell region.

[0100] In some embodiments, the thickness of the core region accounts for 60-99%, preferably 70-98%, and more preferably 80-95% of the thickness of the longitudinal section of the electrode material.

[0101] In the present application, there is no limitation on the method for measuring the thickness of the core region, and the thickness can be measured according to conventional methods in the art, for example, by performing elemental analysis on the cross section of the material using EDS.

[0102] For example, when the electrode material is in rod shape, Figure 1In the embodiment, the thickness of the core region is shown as L1 in FIG. b, which accounts for 60-99%, preferably 70-98%, and more preferably 80-95% of the thickness of the longitudinal section of the nanorod.

[0103] For example, it may account for 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, etc., of the thickness of the longitudinal cross section of the nanorod.

[0104] In some embodiments, the thickness of the shell region accounts for 0.01-40%, preferably 0.01-30%, and more preferably 0.5-20% of the width of the longitudinal section of the electrode material.

[0105] In this application, when the electrode material is a rod-shaped electrode material, such as Figure 1 As shown in b, the thickness of the shell region refers to the sum of the left and right thicknesses excluding the core region on the longitudinal section.

[0106] For example, the thickness of the shell region may be 0.01%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc., of the longitudinal cross-sectional width of the electrode material.

[0107] In some embodiments, the shell region has a certain porosity; preferably, the porosity is 30-70%, preferably 40-65%, and more preferably 45-60%;

[0108] The material with a core-shell structure obtained in the present application has a large catalytic reaction area due to the abundant voids on the surface of the shell region, and the shell layer has multiple catalytic active centers, so that the catalytic activities of hydrogen evolution and oxygen evolution in the catalytic reaction are synergistically improved, thereby improving the electrolysis efficiency. In addition, since the core layer serves as a conductive channel, the electron transmission efficiency can be improved.

[0109] The present application provides a method for preparing an electrode material, which comprises:

[0110] In-situ growth of metal-doped nickel-containing sulfide on the surface of the nickel-containing material;

[0111] treating the surface layer to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer;

[0112] The surface layer of the metal-doped nickel-containing sulfide coated with the nickel oxide layer is treated to obtain an electrode material in which the shell region comprises a nickel-containing compound and the core region comprises metal-doped nickel sulfide.

[0113] In some embodiments, the present application does not impose any restrictions on nickel-containing materials, which can be a nickel substrate or particles containing a nickel element; preferably, when a nickel substrate is used, it is necessary to clean the surface of the nickel substrate, preferably, use a solvent to clean the surface of the nickel substrate, preferably, the solvent can be one or more acid solutions such as sulfuric acid, hydrochloric acid, nitric acid, or alkali solutions such as potassium hydroxide, sodium hydroxide, or organic solvents such as ethanol and acetone.

[0114] In some embodiments, the nickel substrate can be a nickel wire mesh, a porous nickel plate mesh, a nickel alloy mesh, or nickel foam.

[0115] In some embodiments, the method of in-situ growing a metal-doped nickel-containing sulfide on the surface of a nickel-containing material comprises:

[0116] mixing a doping metal source and a sulfur source and dissolving them in a solvent to obtain a precursor solution;

[0117] The precursor solution is mixed with the nickel-containing material for reaction.

[0118] In the present application, the doping metal source is one or more of a vanadium source, an iron source, a molybdenum source, a cobalt source or a tin source. For example, the vanadium source can be vanadium powder, vanadium chloride, sodium vanadate, sodium metavanadate, vanadium pentoxide, sodium vanadate dodecahydrate, etc.; the iron source can be iron powder, ferric chloride, ferric nitrate, ferrous nitrite, ferric sulfate, ferrous sulfate, ferrous oxide, etc.; the molybdenum source can be molybdenum oxide, molybdenum chloride, ammonium molybdate, sodium molybdate, etc.; the cobalt source can be cobalt chloride, cobalt nitrate, cobalt phosphate, cobalt sulfate, cobalt oxide, etc.; the tin source can be tin oxide, tin tetrachloride, sodium stannate, potassium stannate, zinc stannate, metastannic acid, etc.

[0119] In the present application, the sulfur source may be, for example, an organic sulfur source or an inorganic sulfur source. Preferably, the organic sulfur source may be thiourea, thioacetamide or sodium dithionite; preferably, the inorganic sulfur source may be sulfur powder or sulfur dioxide.

[0120] In some embodiments, the solvent is water, ethanol, ethylene glycol, glycerol, etc.

[0121] In some embodiments, in the precursor solution, the molar ratio of the metal in the doping metal source to the sulfur in the sulfur source is 1:0.1-30, preferably 1:0.3-25, and more preferably 1:0.5-20.

[0122] For example, in the precursor solution, the molar ratio of the metal in the doping metal source to the sulfur in the sulfur source (n 钒 :n 硫 ) can be 1:0.1, 1:0.3, 1:0.5, 1:1, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, etc.

[0123] In some embodiments, the concentration of the doping metal source is 1-80 mM, preferably 2-60 mM, and more preferably 3-40 mM, so that the molar ratio of the metal in the doping metal source to the sulfur in the sulfur source in the precursor solution is within the above range.

[0124] For example, in the precursor solution, the concentration of the doping metal source can be 1 mM, 5 mM, 10 mM, 15 mM, 20 mM, 25 mM, 30 mM, 35 mM, 40 mM, 45 mM, 50 mM, 55 mM, 60 mM, 65 mM, 70 mM, 75 mM, 80 mM, etc.

[0125] In some embodiments, mixing the precursor solution with the nickel-containing material for reaction includes: placing the precursor solution and the nickel-containing material in a hydrothermal reactor for mixing and reacting, preferably performing a hydrothermal or solvothermal reaction.

[0126] The hydrothermal reaction refers to a method in which substances in an original mixture react with water as a solvent in a sealed pressure vessel.

[0127] The solvothermal reaction refers to a synthesis method in which substances in the original mixture react in a closed system such as an autoclave, using organic matter or non-aqueous solvent as solvent, at a certain temperature and autogenous pressure of the solution.

[0128] In some embodiments, the reaction is carried out at 90-200° C., preferably 100-180° C.; preferably, the reaction time is 0.2-30 h, preferably 1-10 h.

[0129] For example, the reaction temperature can be 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc.;

[0130] The reaction time can be 0.2h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 15h, 20h, etc.

[0131] In some embodiments, after the reaction, the hydrothermal autoclave is naturally cooled, the material is taken out, and rinsed with ethanol and water to obtain metal-doped nickel-containing sulfide.

[0132] In some embodiments, treating the surface layer to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer comprises: electrochemically oxidizing a nickel-containing material having a surface layer containing a metal-doped nickel-containing sulfide to obtain a metal-doped nickel-containing sulfide, preferably, the deposition voltage of the electrochemical oxidation is 0.2-1.4 V, preferably 0.5-1.3 V, and more preferably 0.6-1.25 V;

[0133] Preferably, the deposition time of electrochemical oxidation is 0.1-60 min, preferably 0.3-30 min, and more preferably 0.4-10 min.

[0134] In some embodiments, in a three-electrode system, a nickel-containing material having a surface layer containing metal-doped nickel sulfide is used as a working electrode, Hg / HgCl2 is selected as a reference electrode, and a carbon rod is used as a counter electrode. Preferably, in an alkaline electrolyte, the surface layer of the metal-doped nickel sulfide material is in situ oxidized under constant potential conditions to form a metal-doped nickel sulfide coated with a nickel oxide layer.

[0135] In the present application, the deposition voltage may be, for example, 0.2V, 0.3V, 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, etc.

[0136] In some embodiments, the deposition time is 0.1-60 min, preferably 0.3-30 min, and more preferably 0.4-10 min.

[0137] For example, the deposition time may be 0.1 min, 0.2 min, 0.3 min, 0.4 min, 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0138] This application adopts electrochemical pre-oxidation technology, and the surface doped metal elements will undergo partial precipitation during the electrolysis process, while the outer layer of nickel-containing sulfide is converted into a nickel oxide layer in situ; by controlling the appropriate electrochemical oxidation voltage and deposition time, a metal-doped nickel-containing sulfide coated with a nickel oxide layer of a certain thickness is obtained.

[0139] In some embodiments, a method for treating the surface layer of a metal-doped nickel-containing sulfide coated with a nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide includes:

[0140] calcining the metal-doped nickel-containing sulfide coated with the nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide, preferably at a calcination temperature of 200-600° C., preferably 250-400° C., and more preferably 300-400° C.;

[0141] Preferably, the calcination time is 0.5-25 h, preferably 1-10 h, and more preferably 2-5 h.

[0142] For example, the calcination temperature may be 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, etc.;

[0143] The calcination time can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 15h, 20h, 25h, etc.

[0144] In some embodiments, when the shell region comprises nickel nitride, the calcination is carried out in an atmosphere containing NH3, wherein the NH3 content in the atmosphere is 10-100%. In addition to ammonia, the atmosphere may contain one or more of hydrogen, argon, nitrogen or helium.

[0145] When the shell region contains nickel phosphide, the calcination is carried out in an inert gas atmosphere using NaH2PO2·H2O as a phosphorus source to phosphate the material at a phosphating temperature of 300-500°C, preferably 350-400°C.

[0146] When the shell region comprises nickel carbide, the calcination is carried out in an atmosphere containing melamine, which may contain one or more of argon, nitrogen or helium, and may also contain 1-5% of hydrogen.

[0147] During the calcination process, as nitrogen molecules diffuse from the outside to the inside into the nickel lattice layer, a gradient nitriding layer will be formed on the electrode. At the above temperature and time, the nickel oxide layer will be completely converted into a nickel-containing compound layer without destroying its structure.

[0148] In some embodiments, the electrode material is the electrode material described above.

[0149] The electrode material prepared by the above method in this application does not require the introduction of an additional template agent. It is obtained by a one-step wet chemical method. By adopting pre-oxidation technology and in-situ nitridation treatment, the micro-nano structure of the material can be maintained, greatly reducing the difficulty and cost of synthesis. At the same time, during the electrochemical pre-oxidation process, the precipitation of the doped metal in the metal-doped nickel sulfide will create abundant pores, increasing the contact area between the electrode and the electrolyte. Then, by controlling the in-situ nitrogen / phosphorus / carbon / sulfurization process, abundant unsaturated nickel high-activity sites are formed on the surface, so that the obtained electrode has a higher electrolysis efficiency.

[0150] The present application provides an electrode composite layer, which comprises a nickel base layer and the electrode material described above or an electrode material prepared by the method described above, wherein the electrode material is arranged on the nickel base layer.

[0151] In this application, when the electrode material is in the shape of a rod, it is arranged on a nickel base layer to form an array electrode. Figure 2 It is an array electrode in a specific embodiment of the present application, wherein a is a central longitudinal section schematic diagram, b is a cross-sectional schematic diagram, 3 is a nickel base layer, and 4 is an array layer formed when the electrode material is rod-shaped.

[0152] In the present application, there is no limitation on the formation of the cross section, which may be a circle or any other shape or an irregular pattern.

[0153] In some embodiments, the thickness of the nickel base layer accounts for 20-90% of the overall longitudinal cross-sectional width of the electrode, preferably 30-85%, and more preferably 40-70%. When the electrode material is rod-shaped and forms an array electrode, the thickness of the nickel base layer accounts for 20-90% of the overall longitudinal cross-sectional width of the electrode, preferably 30-85%, and more preferably 40-70%. Figure 2 The thickness shown in Figure 2 As shown in L in a.

[0154] Preferably, the diameter of the nickel base layer is 100-500 μm, preferably 200-300 μm;

[0155] For example, the thickness of the nickel base layer may account for 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc. of the thickness of the electrode composite layer;

[0156] The diameter of the nickel base layer can be 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, etc.

[0157] In this application, there is no restriction on the method for measuring the thickness of the nickel base layer. It can be measured by conventional methods in the field, such as direct observation and measurement of the cross section of the electrode skeleton unit using a scanning electron microscope or analysis and measurement after EDS surface scanning, to obtain the thickness of the nickel base layer.

[0158] In the present application, the nickel base layer is the main body of the electrode skeleton, and has good mechanical stability and conductivity, and the electrode skeleton unit has good mechanical strength and a large electrochemical effective area.

[0159] In some embodiments, the electrode composite layer forms an electrode having a continuous three-dimensional porous network structure. In the present application, there is no restriction on the form of the network structure, as long as the liquid and gas can diffuse and overflow smoothly on the surface of the electrode. For example, it can be in the form of a mesh, a screen or a foam.

[0160] The electrode composite layer provided in the present application can operate stably for a long time in a strong alkaline electrolyte. Moreover, due to the presence of the above-mentioned highly active core-shell structure catalytic layer, the power consumption required to produce unit volume of hydrogen and oxygen can be reduced compared with existing electrodes.

[0161] The present application provides a method for preparing the electrode composite layer described above. The method is basically the same as the method for preparing the electrode material. When the electrode material is in the shape of a rod, it can be prepared into an array electrode. The preparation process is as follows: Figure 3 shown.

[0162] The present application provides applications of the above-mentioned electrode composite layer in the field of catalysis, including electrocatalytic decomposition of water, electrocatalytic reduction of carbon dioxide, electrocatalytic production of ammonia, electrocatalytic oxidation of pollutants, etc.

[0163] The present application provides applications of the above-mentioned electrode composite layer in the field of electrochemistry, including supercapacitors, ion batteries, etc.

[0164] Example

[0165] This application provides general and / or specific descriptions of the materials and experimental methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., percentage by weight. All reagents or instruments used without manufacturer indication are commercially available conventional reagents.

[0166] Example 1

[0167] according to Figure 3 The steps shown are as follows:

[0168] (1) Select an area of 2×3cm 2 A nickel wire mesh with a mesh size of 50 and a wire diameter of 250 μm was used as the base material, and the base surface was cleaned with acetone, dilute sulfuric acid and ethanol to remove surface organic matter and oxide layer.

[0169] (2) Using sodium vanadate as the vanadium source and thiourea as the sulfur source, 0.75 mmol of sodium vanadate was added to 35 ml of anhydrous ethanol at a molar ratio of 1:2. The mixture was magnetically stirred at room temperature for 3 minutes to obtain suspension A, i.e., the precursor solution. Suspension A and the cleaned nickel substrate were placed in a 50 mL hydrothermal autoclave and subjected to a solvothermal reaction at 120°C for 5 hours. After the autoclave was cooled naturally, the resulting material was removed, rinsed with ethanol and water, and vacuum-dried for later use to obtain vanadium-doped nickel sulfide.

[0170] (3) In a three-electrode system, Hg / HgCl2 is selected as the reference electrode, a carbon rod is used as the counter electrode, and the nickel mesh substrate with vanadium-doped nickel sulfide grown on the surface obtained in step (2) is used as the working electrode. Electrochemical oxidation is carried out in 1M KOH alkaline electrolyte at a constant potential of 0.8 V for 24 seconds to obtain nickel oxide-coated vanadium-doped nickel sulfide.

[0171] (4) The nickel oxide-coated vanadium-doped nickel sulfide obtained in the previous step is placed in a tube furnace, and the calcination temperature is controlled to be 350°C in a 90% NH3 / 10% H2 atmosphere. After calcination for 20 minutes, the material is rapidly cooled to room temperature and taken out to obtain an electrode material in which the shell region comprises nickel nitride and the core region comprises vanadium-doped nickel sulfide. The electrode material is in the shape of a rod, and the rod shape is relatively uniform. The diameter of the rod generally decreases gradually from the base to the direction away from the base, and the cross-sectional shape of the nanorod is nearly circular.

[0172] The resulting electrode material was formed into an array electrode. The electrode had a wire mesh structure with a circular cross-section and a wire diameter of 255 μm. In the array electrode, the nickel metal base layer was approximately 240 μm thick, and the electrode material grown on the surface of the nickel base was approximately 15 μm thick.

[0173] Energy dispersive X-ray spectroscopy (EDS) analysis of individual electrode materials using a transmission electron microscope revealed that vanadium and sulfur are primarily concentrated in the center of the electrode material, nickel is distributed throughout the electrode material, nitrogen is located on the surface, and vanadium is almost non-existent on the surface. The thickness of the vanadium-doped nickel sulfide layer, measured from fine to coarse, ranges from 0.1 to 0.26 μm, while the average thickness of the nickel nitride layer in the shell region is 10 nm.

[0174] TEM line scans revealed a vanadium content of approximately 3-4% molar in the core region. X-ray spectroscopy (XPS) scans of the bulk sample surface revealed a nitrogen content of 32-35% molar, with the vanadium content being virtually zero molar. After argon ion etching of 30 nm, the XPS nitrogen content dropped to less than 10%, while the vanadium content rose to approximately 2%. Since vanadium is generally susceptible to oxidation, it is speculated that a mixed valence of vanadium (+3, +4, and +5) was detected here.

[0175] Raman spectroscopy can detect the presence of broadened VS bonds and Ni-O bonds, which come from amorphous and low-crystallinity vanadium sulfide and nickel oxide. X-ray diffraction and high-magnification transmission electron microscopy analysis of the sample phase and crystallinity detected strong nickel and Ni3S2, weaker NiS and weaker Ni4N and Ni3N lattice diffraction peaks and corresponding interplanar spacing distribution. In addition, the peak calibration in the XPS spectrum of S obtained that the peak at 164.5eV is attributed to S2 2- unsaturated sulfur sites.

[0176] Example 2

[0177] The preparation method is the same as that of Example 1, except that: in step (1) and step (2), 1 mmol of nickel powder is added as a raw material without further treatment; in step (3), the obtained vanadium-nickel sulfide powder is prepared into a slurry and applied to the surface of a glassy carbon electrode for use as a working electrode: 10 mg of vanadium-nickel sulfide powder is added to 100 μl of isopropanol and 20 μl of Nafion, mixed, and then dropped onto the surface of the glassy carbon electrode to dry and form a film.

[0178] The structures of the obtained electrode material and electrode composite layer are similar to those of Example 1.

[0179] Example 3

[0180] The preparation method of Example 3 is the same as that of Example 1, except that the nickel substrate used in step (1) is 2×3 cm 2 , nickel foam with a thickness of 1 mm, a pore size of 230 μm and a porosity of 96%.

[0181] The obtained electrode material and electrode composite layer have similar structures to those in Example 1.

[0182] Example 4

[0183] The preparation method of Example 4 is the same as that of Example 1, except that the reaction conditions of step 3 and step 4 are 0.8 V, 200 s and 350° C., 40 min, respectively.

[0184] The electrode composite layer and the electrode material with a core-shell structure obtained in Example 4 have similar structures to those in Example 1, except that the nickel nitride shell layer of the single electrode material is thicker, with an average thickness of 15 nm.

[0185] Example 5

[0186] The preparation method of Example 5 is similar to that of Example 1, except that: the vanadium source selected in step (2) is sodium vanadate dodecahydrate, the sulfur source is thioacetamide, the hydrothermal temperature is 160°C, the conditions of step (3) are 0.8V, 300s; the conditions of step (4) are 350°C, 20min, and the calcination atmosphere is pure NH3 atmosphere.

[0187] The structure of the electrode composite layer and the structure of the electrode material obtained in Example 5 are similar to those in Example 1, but the electrode wire diameter obtained in Example 5 is larger, about 300 μm, and the diameter of the central nickel layer is about 230 μm.

[0188] Example 6

[0189] Same as Example 1, except that the hydrothermal precursors consisted of 1 mmol of ammonium molybdate, 4 mL of aqueous ammonia, 40 mL of deionized water, 5.3 mmol of thioacetamide, and the same nickel mesh as in Example 1. The hydrothermal temperature was 200°C for 12 hours. Subsequent processing was the same as in Example 1, resulting in a molybdenum-doped nickel sulfide-nickel nitride nanorod core-shell structure electrode material and the corresponding electrode composite layer.

[0190] Example 7

[0191] Same as Example 1, except that the hydrothermal precursors consisted of 0.15 mmol thiourea, 0.15 mmol ferric sulfate, 35 mL deionized water, and the same nickel substrate as in Example 1, and the mixture was hydrothermally heated at 150°C for 12 h. Subsequent steps were the same as in Example 1, resulting in an iron-doped nickel sulfide-nickel nitride core-shell electrode material and the corresponding electrode composite layer.

[0192] Example 8

[0193] Same as Example 1, except that the hydrothermal precursors consisted of 1 mmol of cobalt nitrate, 3.5 g of sodium sulfide, 0.1 g of urea, 0.04 g of sodium citrate, 40 mL of deionized water, and the same nickel substrate as in Example 1. The hydrothermal temperature and time were 160°C and 12 h, respectively. The resulting electrode material was a cobalt-doped nickel sulfide-nickel nitride core-shell structure and the corresponding electrode composite layer.

[0194] Example 9

[0195] The same as Example 1, except that when the obtained vanadium-doped nickel sulfide is treated in a tube furnace after anodization, 1.5 g of sodium dihydrogen phosphate powder is placed upstream of the air flow in the tube furnace, argon is passed through, and the temperature is raised to 350°C at 5°C / min, kept constant for 15 minutes, and then rapidly cooled. The vanadium-doped nickel sulfide-nickel phosphide core-shell structure electrode material and the corresponding electrode composite layer are obtained.

[0196] Example 10

[0197] The same as Example 1, except that when the obtained vanadium-doped nickel sulfide is treated in a tube furnace after anodization, 1.0 g of elemental sulfur powder is placed upstream of the air flow in the tube furnace, argon is passed through, and the temperature is raised to 300°C at 5°C / min, kept constant for 10 minutes, and then rapidly cooled. The vanadium-doped nickel sulfide-nickel sulfide core-shell structure electrode material and the corresponding electrode composite layer are taken out.

[0198] Example 11

[0199] The same as Example 1, except that when the obtained vanadium-doped nickel sulfide is treated in a tube furnace after anodization, 0.5 g of melamine powder is placed upstream of the air flow in the tube furnace, and 5% H2 / Ar is passed through. The temperature is raised to 600°C at 5°C / min, maintained constant for 20 minutes, and then rapidly cooled. The vanadium-doped nickel sulfide-nickel carbide core-shell structure electrode material and the corresponding electrode composite layer are taken out.

[0200] Comparative Example 1

[0201] 7.5 mL of 2 mol / L nickel acetate tetrahydrate (C4H6O4Ni·4H2O) aqueous solution and 7.5 mL of 2 mol / L sodium hydroxide (NaOH) aqueous solution were measured and added to 35 mL of ultrapure water in sequence and magnetically stirred for 1 h. Then, the mixture was placed in a 50 mL reactor and the same nickel substrate as in the example was added. Ni(OH)2 nanowire arrays were synthesized on the surface of the substrate by a hydrothermal method at 120°C for 24 h. The Ni3N nanowire arrays and corresponding electrodes were then obtained by calcining at 350°C in an ammonia atmosphere for 2 h.

[0202] Comparative Example 2

[0203] The preparation method is the same as that of Example 1, except that the obtained vanadium-doped nickel sulfide is not subjected to subsequent anodic oxidation and nitridation treatment, and a pure vanadium-doped nickel sulfide electrode material and a corresponding electrode are obtained.

[0204] Comparative Example 3

[0205] The same as Example 6, but without subsequent anodization and nitriding treatment, the obtained material is a simple molybdenum-doped nickel sulfide electrode material and a corresponding electrode.

[0206] Comparative Example 4

[0207] The same as Example 7, but without the subsequent anodic oxidation and nitriding treatment, the obtained material is a pure iron-doped nickel sulfide electrode material and a corresponding electrode.

[0208] Comparative Example 5

[0209] The same as Example 8, but without subsequent anodization and nitridation treatment, the obtained material is a simple cobalt-doped nickel sulfide electrode material and a corresponding electrode.

[0210] Comparative Example 6

[0211] The same as Comparative Example 1, but the tubular furnace atmosphere treatment is the same as the phosphating treatment in Example 9, the phosphating time is 2 hours, and then naturally cooled, to obtain a nickel phosphide electrode material and a corresponding electrode.

[0212] Comparative Example 7

[0213] The same as Comparative Example 1, but the atmosphere treatment in the tube furnace is the same as the sulfurization treatment in Example 10, the sulfurization time is 2 hours, and then naturally cooled, to obtain nickel sulfide electrode material and corresponding electrode.

[0214] Comparative Example 8

[0215] The same as Comparative Example 1, but the atmosphere treatment in the tubular furnace is the same as the carbonization treatment in Example 11, the carbonization time is 2 hours, and then naturally cooled, to obtain nickel sulfide electrode material and corresponding electrode.

[0216] Experimental example

[0217] The above embodiment and comparative example electrodes were used as working electrodes in a three-electrode system. The electrolyte was 1M KOH, the counter electrode was a carbon rod, and the reference electrode was a Hg / HgO electrode. The different electrodes were tested at room temperature under the conditions of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with a fixed current of 100 mA / cm 2 The initial overpotential after stabilization within the first 10 minutes of the reaction and the change in overpotential after 48 hours of testing (corrected by IR) are shown in Table 1. At the same current density, the lower the overpotential, the better the performance of the electrode material.

[0218] Note: Since Example 2 is a powder material, it needs to be made into a membrane electrode on a 3mm diameter glassy carbon electrode. The overpotential measured by this method at the same current density will be higher than that of the formed electrodes of other examples.

[0219] Table 1 Overpotential of different electrodes

[0220]

[0221] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application in any other manner. Any person skilled in the art may utilize the above disclosed technical content to modify or modify the present application into equivalent embodiments with equivalent variations. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present application and are based on the technical essence of the present application shall still fall within the scope of protection of the present application.

Claims

1. An electrode material having a core-shell structure, wherein: The core region of the electrode material comprises metal-doped nickel sulfide, and the shell region comprises a nickel-containing compound; The metal of the metal-doped nickel sulfide is one or more of vanadium, molybdenum, iron, cobalt, and tin; The nickel-containing compound comprises one of nickel nitride, nickel carbide, nickel sulfide or nickel phosphide; The nickel-containing compound is obtained by in-situ nitriding, carbonization, sulfiding or phosphating; The shell region has open pores with an average porosity of 20-70%.

2. The electrode material according to claim 1, wherein The shell region of the material further contains other metal elements for doping, and the other metal elements are selected from one or more of molybdenum, vanadium, iron, cobalt, copper, tungsten and ruthenium.

3. The electrode material according to claim 1, wherein The molar content of the doped metal in the metal-doped nickel sulfide gradually decreases from the center of the material to the outside.

4. The electrode material according to claim 3, wherein The molar content of the doping metal in the region close to the shell region is less than 10%.

5. The electrode material according to claim 3, wherein The molar content of the doping metal in the region close to the shell region is less than 7%.

6. The electrode material according to claim 3, wherein The molar content of the doping metal near the center of the material is 5-40%.

7. The electrode material according to claim 3, wherein The molar content of the doping metal near the center of the material is 8-30%.

8. The electrode material according to claim 3, wherein The molar content of the doping metal near the center of the material is 10-25%.

9. The electrode material according to claim 1, wherein the average porosity is 30-65%.

10. The electrode material according to claim 1, wherein the average porosity is 35-60%.

11. The electrode material according to any one of claims 1 to 8, wherein The core region comprises vanadium-nickel sulfide, elemental nickel and nickel oxide; The vanadium-nickel sulfide comprises Ni3S 2、 Unsaturated vanadium sulfide and NiS.

12. The electrode material according to claim 11, wherein In terms of mass percentage in the vanadium-nickel sulfide, the Ni3S2 is 10-70%; The unsaturated vanadium sulfide is 1-30%.

13. The electrode material according to claim 11, wherein Calculated by mass percentage in the vanadium-nickel sulfide, the Ni3S2 is 20-60%; The unsaturated vanadium sulfide is 2-20%.

14. The electrode material according to claim 11, wherein Calculated by mass percentage in the vanadium-nickel sulfide, the Ni3S2 is 25-50%; The unsaturated vanadium sulfide is 3-10%.

15. The electrode material according to any one of claims 1 to 8, wherein The shell region comprises nickel nitride, nickel oxide and vanadium nitride, and the nickel nitride comprises nickel nitride and / or unsaturated nitrided nickel.

16. The electrode material according to claim 15, wherein The nitrogen molar content in the shell region gradually decreases from the shell region to the core region.

17. The electrode material according to claim 16, wherein The nitrogen molar content of the shell region near the core region is less than 10%.

18. The electrode material according to claim 16, wherein The nitrogen molar content of the shell region near the core region is less than 5%.

19. The electrode material according to any one of claims 1 to 8, wherein The electrode material has the morphology of nanorods, nanosheets or nanospheres.

20. The electrode material according to claim 19, wherein The thickness of the core region accounts for 60-99% of the thickness of the longitudinal section of the electrode material.

21. The electrode material according to claim 19, wherein The thickness of the core region accounts for 70-98% of the thickness of the longitudinal section of the electrode material.

22. The electrode material according to claim 19, wherein The thickness of the core region accounts for 80-95% of the thickness of the longitudinal section of the electrode material.

23. The electrode material according to claim 19, wherein The thickness of the shell region accounts for 0.01-40% of the width of the longitudinal section of the electrode material.

24. The electrode material according to claim 19, wherein The thickness of the shell region accounts for 0.01-30% of the width of the longitudinal section of the electrode material.

25. The electrode material according to claim 19, wherein The thickness of the shell region accounts for 0.5-20% of the width of the longitudinal section of the electrode material.

26. A method for preparing an electrode material, comprising: In-situ growth of metal-doped nickel-containing sulfide on the surface of the nickel-containing material; treating the surface layer to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer; Treating the surface of the metal-doped nickel-containing sulfide coated with the nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide; The method of treating the surface layer to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer comprises: electrochemically oxidizing a nickel-containing material having a surface layer containing a metal-doped nickel-containing sulfide to obtain a metal-doped nickel-containing sulfide coated with a nickel oxide layer; The method of treating the surface layer of the metal-doped nickel-containing sulfide coated with the nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide comprises: calcining the metal-doped nickel-containing sulfide coated with the nickel oxide layer to obtain an electrode material having a shell region comprising a nickel-containing compound and a core region comprising a metal-doped nickel sulfide; The metal of the metal-doped nickel sulfide is one or more of vanadium, molybdenum, iron, cobalt, and tin; The nickel-containing compound comprises one of nickel nitride, nickel carbide, nickel sulfide or nickel phosphide.

27. The method according to claim 26, wherein The method for in-situ growing metal-doped nickel-containing sulfide on the surface of a nickel-containing material comprises: mixing a doping metal source and a sulfur source and dissolving them in a solvent to obtain a precursor solution; The precursor solution is mixed with the nickel-containing material for reaction.

28. The method according to claim 26, wherein The doping metal source is one or more of a vanadium source, an iron source, a molybdenum source, a cobalt source or a tin source.

29. The method according to claim 28, wherein The doping metal source is a vanadium source, and the vanadium source is vanadium powder, vanadium chloride, sodium vanadate, sodium metavanadate, vanadium pentoxide or sodium vanadate dodecahydrate.

30. The method according to claim 29, wherein The concentration of the vanadium source is 1-80 mM.

31. The method according to claim 29, wherein The concentration of the vanadium source is 2-60 mM.

32. The method of claim 29, wherein: The concentration of the vanadium source is 3-40 mM.

33. The method of claim 27, wherein: In the precursor solution, the molar ratio of the metal source in the doping metal source to the sulfur in the sulfur source is 1:0.1-30.

34. The method of claim 27, wherein: In the precursor solution, the molar ratio of the metal source in the doping metal source to the sulfur in the sulfur source is 1:0.3-25.

35. The method of claim 27, wherein: In the precursor solution, the molar ratio of the metal source in the doping metal source to the sulfur in the sulfur source is 1:0.5-20.

36. The method of claim 27, wherein: In the precursor solution, the sulfur source is an inorganic sulfur source or an organic sulfur source.

37. The method according to claim 36, wherein The inorganic sulfur source is sulfur dioxide or sodium dithionite; the organic sulfur source is thiourea or thioacetamide.

38. The method of claim 27, wherein: The solvent is water, ethanol, ethylene glycol or glycerol.

39. The method of claim 27, wherein: The reaction of mixing the precursor solution with the nickel-containing material includes: The precursor solution and the nickel-containing material are placed in a hydrothermal reactor for mixing and reaction.

40. The method of claim 39, wherein The precursor solution and the nickel-containing material are placed in a hydrothermal kettle for hydrothermal or solvothermal reaction.

41. The method of claim 39, wherein The reaction is carried out at 90-200°C.

42. The method of claim 39, wherein: The reaction is carried out at 100-180°C.

43. The method of claim 39, wherein: The reaction time is 0.2-30h.

44. The method of claim 39, wherein The reaction time is 1-10h.

45. The method of claim 26, wherein The deposition voltage of electrochemical oxidation is 0.2-1.4V.

46. The method of claim 26, wherein the deposition voltage of the electrochemical oxidation is 0.5-1.3V.

47. The method of claim 26, wherein the deposition voltage of the electrochemical oxidation is 0.6-1.25V.

48. The method of claim 26, wherein The deposition time of electrochemical oxidation is 0.1-60min.

49. The method of claim 26, wherein The deposition time of electrochemical oxidation is 0.3-30min.

50. The method of claim 26, wherein The deposition time of electrochemical oxidation is 0.4-10min.

51. The method of claim 26, wherein: The calcination temperature is 200-600°C.

52. The method of claim 26, wherein: The calcination temperature is 250-400°C.

53. The method of claim 26, wherein: The calcination temperature is 300-400℃.

54. The method of claim 26, wherein: The calcination time is 0.5-25h.

55. The method of claim 26, wherein The calcination time is 1-10h.

56. The method of claim 26, wherein: The calcination time is 2-5h.

57. The method of claim 26, wherein: The nickel-containing material is a nickel substrate or particles containing nickel alone.

58. The method of claim 57, wherein When the nickel-containing material is a nickel substrate, the surface of the nickel substrate needs to be cleaned.

59. The method according to any one of claims 26 to 58, wherein The electrode material is the electrode material according to any one of claims 2 to 25.

60. An electrode composite layer comprising a nickel base layer and the electrode material according to any one of claims 1 to 25 or the electrode material prepared by the method according to any one of claims 26 to 59, wherein the electrode material is disposed on the nickel base layer.

61. The electrode composite layer according to claim 60, wherein The thickness of the nickel base layer accounts for 20-90% of the thickness of the electrode material.

62. The electrode composite layer according to claim 60, wherein The thickness of the nickel base layer accounts for 30-85% of the thickness of the electrode material.

63. The electrode composite layer according to claim 60, wherein The thickness of the nickel base layer accounts for 40-70% of the thickness of the electrode material.

64. The electrode composite layer according to claim 60, wherein The porosity of the nickel base layer is less than 5%.

65. The electrode composite layer according to claim 60, wherein The porosity of the nickel base layer is less than 2%.

66. The electrode composite layer according to claim 60, wherein The diameter of the nickel base layer is 100-500 μm.

67. The electrode composite layer according to claim 60, wherein The diameter of the nickel base layer is 200-300 μm.

68. The electrode composite layer according to claim 60, wherein The pore size of the nickel base layer is 0.02-2.0 mm.

69. The electrode composite layer according to claim 60, wherein The pore size of the nickel base layer is 0.2-1 mm.

70. Use of the electrode composite layer according to any one of claims 60 to 69 in the field of catalysis.

71. The use according to claim 70, wherein The catalytic field is electrocatalytic decomposition of water or electrocatalytic reduction of carbon dioxide.

72. Use of the electrode composite layer according to any one of claims 60 to 69 in the field of electrochemistry.

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