A nickel-containing electrode, a method of making and use thereof

Abstract

The application discloses a nickel-containing electrode, a preparation method and application thereof. The nickel-containing electrode comprises a nickel-containing metal layer and a nickel-containing nitride layer from inside to outside. The molar content of nitrogen in the nickel-containing nitride layer increases first and then decreases from inside to outside in the direction away from the nickel-containing metal layer. The nickel-containing electrode has high active sites on the surface, and the performance of the high active sites is close to that of a noble metal platinum. Under the condition of additional voltage and other conditions being consistent, the electrode has higher hydrogen production rate than a current metal nickel or nickel alloy electrode. Compared with a surface layer particle type electrode, the electrode has higher unit mass activity and higher stability due to the three-dimensional independent integrated configuration. In addition, the electrode has simple synthesis process, economical raw materials, low overall manufacturing cost and high large-scale application potential.

Description

Technical Field

[0001] This application relates to the field of electrode technology, and in particular to a nickel-containing electrode rich in highly active nitrogen defect sites, its preparation method, and its application. Background Technology

[0002] Hydrogen production via water electrolysis using renewable energy is a green and sustainable method. Alkaline water electrolysis is currently the mainstream technology in China due to its lower cost and ease of large-scale production. In an alkaline electrolyte, the cathode hydrogen production process primarily involves the activation and dissociation of water molecules on the electrode surface, generating hydrogen atoms adsorbed at the active sites. Two adsorbed hydrogen atoms then combine and dissociate to generate hydrogen gas, or one adsorbed hydrogen atom reacts with a water molecule and an electron to produce hydrogen molecules. For this reaction to proceed rapidly, the electrolysis cathode must possess not only high electrical conductivity but also superior catalytic activity for water splitting to produce hydrogen.

[0003] The difference between the adsorption and desorption energies of hydrogen atoms is a crucial parameter for determining the electrocatalytic activity of electrode materials in water splitting for hydrogen production. The closer the difference between the adsorption and desorption energies of hydrogen atoms on the electrode surface is to zero, the higher its catalytic activity for hydrogen production. Platinum, a noble metal, exhibits a hydrogen adsorption-desorption energy difference very close to zero, making it the electrode material with the highest electrocatalytic activity for hydrogen production currently available. However, due to the scarcity and high cost of noble metals, existing alkaline electrolyzer cathode materials are mainly based on cheaper transition metals such as nickel, iron, and cobalt. While these electrodes are more economical, their surface activity for water splitting for hydrogen production is far lower than that of noble metals, resulting in higher overpotentials and greater power consumption during the hydrogen production process. Developing economical and efficient electrodes is a key challenge in current water splitting for hydrogen production technology.

[0004] Recent studies have shown that the adsorption-desorption energy difference between nitrogen defect sites and protons in non-noble metal transition compounds like nickel nitride is very close to zero, exhibiting catalytic activity close to that of platinum in alkaline electrolytes. However, existing nitrogen-defect-containing nickel electrode catalytic materials mainly exist in particulate form. For example, Bin Liu et al. disclosed a surface-layer Ni3N-containing material prepared under relatively low-temperature conditions (300℃) using microwave nitrogen plasma bombardment. 1-xParticle-layered nickel foam electrodes (Bin Liu et al., Unconventional Nickel Nitride Enriched with Nitrogen Vacancies as a High-Efficiency Electrocatalyst for Hydrogen Evolution, doi:10.1002 / advs.201800406); Huanyu Jin et al. disclosed a method to obtain surface-unsaturated nitrided nickel particle materials by calcining an organonitrile precursor in an ammonia atmosphere and utilizing the carbon layer formed on the surface to suppress the degree of nickel nitridation (Stable and HighlyEfficient Hydrogen Evolution from Seawater Enabled by an Unsaturated NickelSurface Nitride, doi: / 10.1002 / adma.202007508). In actual hydrogen production processes, these particulate catalytically active materials are prone to detachment from the electrode surface, resulting in poor overall catalytic stability of the electrode. Furthermore, the aforementioned existing synthesis processes all employ relatively mild reaction conditions to suppress sufficient nickel nitridation to obtain nitrogen defects, making it difficult to guarantee the chemical stability of the Ni-N bonds formed in the resulting material. Summary of the Invention

[0005] To address the problem of poor catalytic stability in existing particulate catalytic active materials, this application provides a nickel-containing electrode rich in highly active nitrogen defect sites, its preparation method, and its application. The provided nickel-containing electrode is three-dimensionally independent, structurally stable, and its surface layer is rich in highly active nitrogen defect sites. The nickel-containing electrode not only has higher activity per unit mass but also higher stability.

[0006] The specific technical solution of this application is as follows:

[0007] 1. A nickel-containing electrode, wherein the nickel-containing electrode comprises, from the inside out, a nickel-containing metal layer and a nickel-containing nitride layer, wherein the molar content of nitrogen in the nickel-containing nitride layer first increases and then decreases from the inside out along a direction away from the nickel-containing metal layer.

[0008] 2. The nickel-containing electrode according to claim 1, wherein the nickel-containing nitride layer has open pores, and its porosity gradually increases along the direction away from the nickel-containing metal layer.

[0009] 3. The nickel-containing electrode according to claim 1, wherein the total thickness of the nickel-containing nitride layer accounts for 10-50% of the total thickness of the nickel-containing electrode, preferably 20-40%, and more preferably 25-35%.

[0010] 4. The nickel-containing electrode according to item 1, wherein the molar content of nitrogen in the region between the nickel-containing nitride layer region near the nickel-containing metal layer and the nickel-containing nitride layer surface region away from the nickel-containing metal layer is 10-30%, preferably 12-22%, and more preferably 12-15%.

[0011] 5. The nickel-containing electrode according to any one of items 1-4, wherein the nickel-containing nitride layer comprises Ni3N, unsaturated nickel nitride, and metallic nickel.

[0012] 6. The nickel-containing electrode according to claim 5, wherein the nickel-containing nitride layer further comprises Ni4N.

[0013] 7. The nickel-containing electrode according to claim 1, wherein the molar content of nickel relative to all metal elements in the nickel-containing nitride layer is 50-100%; preferably, when the molar content of nickel in the nickel-containing nitride layer is less than 100%, the nickel-containing nitride layer further includes other metals, wherein the other metals are selected from one or more of molybdenum, copper, cobalt, iron, tungsten and ruthenium.

[0014] 8. The nickel-containing electrode according to any one of items 1-7, wherein the thickness of the nickel-containing metal layer accounts for 50-90% of the thickness of the nickel-containing electrode, preferably 50-80%, and more preferably 60-70%.

[0015] 9. The nickel-containing electrode according to any one of items 1-8, wherein the porosity of the surface region of the nickel-containing nitride layer away from the nickel-containing metal layer is 40-70%, preferably 50-60%.

[0016] 10. The nickel-containing electrode according to any one of claims 1-9, wherein the porosity of the nickel-containing metal layer is less than 5%, preferably less than 2%.

[0017] 11. The nickel-containing electrode according to any one of items 1-10, wherein the nickel-containing metal layer is nickel or contains a metal element other than nickel, preferably, the metal element other than nickel is selected from one or more of molybdenum, vanadium, iron, cobalt, copper, tungsten and ruthenium.

[0018] 12. The nickel-containing electrode according to any one of items 1-11, wherein the thickness of the nickel-containing electrode is 200 μm-2 mm, preferably 300 μm-1 mm.

[0019] 13. The nickel-containing electrode according to any one of items 1-12, wherein the nickel-containing electrode is in the form of a wire mesh, a porous plate mesh, or a foam.

[0020] 14. The nickel-containing electrode according to claim 13, wherein the nickel-containing electrode is in the form of a wire mesh, and the diameter of the nickel-containing electrode is 200-500 μm, preferably 250-450 μm, and more preferably 300-400 μm.

[0021] 15. A method for preparing a nickel-containing electrode, comprising:

[0022] (1) Provide nickel-containing framework network materials;

[0023] (2) The surface layer of the nickel-containing framework network material is converted in situ into a nickel-containing nitride layer to obtain a nickel-containing framework network material with a nickel-containing nitride layer on the surface.

[0024] (3) The nickel-containing nitride layer is partially decomposed to form a porous structure to obtain a nickel-containing electrode.

[0025] 16. The method according to item 15, wherein, in step (3), the decomposition temperature of partially decomposing the nickel-containing nitride layer on the surface to form a porous structure is above 400°C, preferably 450-850°C, and more preferably 550-650°C;

[0026] Preferably, the decomposition time is 0.1-45h, more preferably 0.5-24h, and even more preferably 0.5-12h.

[0027] 17. The method according to item 15, wherein, in step (2), the surface layer of the nickel-containing skeleton network material is subjected to ammonia atmosphere nitriding or ion nitriding to obtain a nickel-containing skeleton network material with a nickel metal nitride layer on the surface;

[0028] Preferably, the nitriding temperature is below 400°C, more preferably 350-400°C, and even more preferably 350-380°C.

[0029] 18. The method according to claim 17, wherein the ammonia atmosphere in the ammonia atmosphere nitriding is generated by an amino-containing substance, preferably by ammonia, hydrazine, urea, dicyandiamide or melamine.

[0030] 19. The method according to item 17, wherein the nitrogen plasma source in the ion nitridation contains nitrogen, ammonia, or hydrazine.

[0031] 20. The method according to item 17, wherein steps (2) and (3) are repeated 1-20 times, preferably 2-15 times, and more preferably 5-10 times.

[0032] 21. The method according to item 17, wherein in step (2), one side of the surface of the nickel-containing skeleton network material is converted in situ into a nickel-containing nitride layer, while the other side is not nitrided.

[0033] 22. A nickel-containing electrode, prepared according to any one of claims 15-21.

[0034] 23. The nickel-containing electrode according to item 22, wherein the nickel-containing electrode is any one of items 1-14.

[0035] 24. The application of the nickel-containing electrode as described in any one of items 1-14 or any one of items 22-23 in the field of catalysis.

[0036] 25. According to the application of item 24, the nickel-containing electrode is used for reactions involving catalytic hydrogen evolution, catalytic oxygen evolution, catalytic hydrogen oxidation, or catalytic oxygen reduction.

[0037] 26. An electrochemical cell comprising a nickel-containing electrode as described in any one of items 1-14 or a nickel-containing electrode as described in any one of items 22-23.

[0038] The effects of the invention

[0039] The nickel-containing electrode provided in this application is easy to scale up for application because its size is an adjustable three-dimensional structure.

[0040] The nickel-containing electrode provided in this application has a surface rich in highly active sites with properties similar to those of the noble metal platinum. Under the same applied voltage and other conditions, this electrode has a higher hydrogen yield than existing metallic nickel or nickel alloy electrodes. Compared with surface particulate electrodes, this electrode has not only higher activity per unit mass but also higher stability due to its three-dimensional independent integrated configuration. In addition, the electrode has a simple synthesis process, economical raw materials, and low overall manufacturing cost, and has high potential for large-scale application. Attached Figure Description

[0041] Figure 1 This is a schematic cross-sectional view of the nickel-containing electrode obtained in Example 1, where a is a schematic cross-sectional view and b is a schematic central longitudinal section view.

[0042] Figure 2 This is a schematic cross-sectional view of the nickel-containing electrode obtained in Example 2, where a is a schematic cross-sectional view and b is a schematic central longitudinal section view.

[0043] Wherein, 1-nickel-containing metal layer, 2-nitride layer Detailed Implementation

[0044] The present application will now be described in detail with reference to the accompanying drawings, wherein the same numerals in all the drawings denote the same features. While specific embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0045] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0046] This application provides a nickel-containing electrode, which comprises a nickel-containing metal layer and a nickel-containing nitride layer from the inside to the outside. The molar content of nitrogen in the nickel-containing nitride layer first increases and then decreases from the inside to the outside in the direction away from the nickel-containing metal layer.

[0047] In this application, the distinction between the nickel-containing metal layer and the nickel-containing nitride layer is based on the molar content of nitrogen. In some embodiments, there is no clear interface between the nickel-containing metal layer and the nickel-containing nitride layer. In some embodiments, the nickel-containing metal layer has a nitrogen molar content of no more than 0.1% relative to the molar content of all elements in the layer, and the nickel-containing nitride layer has a nitrogen molar content of more than 0.1% relative to the molar content of all elements in the layer. Figure 1 As shown in a and b, where, Figure 1 a is a schematic diagram of the cross-section. Figure 1 b is a schematic diagram of the central longitudinal section, 1 is the nickel-containing metal layer, and 2 is the nickel-containing nitride layer.

[0048] In some embodiments, the present application does not impose any restrictions on the method for determining the nitrogen molar content, which can be determined by conventional methods in the art, such as X-ray energy dispersive spectroscopy (EDS) scanning analysis.

[0049] In some embodiments, this application does not impose any restrictions on the shape of the cross-section of the nickel-containing electrode; its cross-section can be any regular or irregular shape, such as a circle or a rhombus, etc. Figure 1 The circles shown and Figure 2 The rhombus shown.

[0050] In some embodiments, the nickel-containing nitride layer has open pores, and its porosity gradually increases along the direction away from the nickel-containing metal layer.

[0051] In this application, the nickel-containing nitride layer has open pores, which can increase the catalytic reaction area.

[0052] In this application, no restrictions are placed on the determination of porosity in nickel-containing nitride layers. Porosity can be determined by conventional methods in the art. For example, scanning electron microscopy can be used to take images, and the porosity can be obtained by calculating the proportion of the area of ​​the pore region to the total area in the image using image processing software. Furthermore, the surface layer can be removed by ion etching, and the porosity at different depths can be analyzed.

[0053] In some embodiments, the porosity of the nickel-containing nitride layer region near the nickel-containing metal layer is 0-10%, preferably 3-5%;

[0054] Preferably, the porosity of the surface region of the nickel-containing nitride layer away from the nickel-containing metal layer is 40-70%, more preferably 50-60%.

[0055] like Figure 1 As shown, the porosity of the nickel-containing nitride layer 2 gradually increases from the inside to the outside, that is, the porosity of the surface layer of the nickel-containing nitride layer 2 is higher, while the porosity of the nickel-containing nitride layer 2 is lower the closer it is to the nickel-containing metal layer 1.

[0056] For example, the porosity of the nickel-containing nitride layer 2 region near the nickel-containing metal layer 1 can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0057] The porosity of the surface region of the nickel-containing nitride layer 2, which is far from the nickel-containing metal layer 1, can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.

[0058] In this application, the nickel-containing nitride layer region near the nickel-containing metal layer refers to the layer whose boundary is a nickel-containing metal interface, accounting for 20% of the total volume of the nickel-containing nitride layer.

[0059] The surface region of the nickel-containing nitride layer that is far from the nickel-containing metal layer refers to the region whose boundary at one end accounts for 20% of the total volume of the nickel-containing nitride layer.

[0060] In some embodiments, the pores in the nickel-containing nitride layer can have an irregular morphology. In some embodiments, the average opening size of the pores is 0.1-10 μm, preferably 0.2-8 μm, and more preferably 0.2-5 μm.

[0061] In this application, the average size of the hole is measured by taking a scanning electron microscope image of the nitride layer.

[0062] In some embodiments, the total thickness of the nickel-containing nitride layer accounts for 10-50% of the total thickness of the nickel-containing electrode, preferably 20-40%, and more preferably 25-35%.

[0063] For example, the thickness of the nickel-containing nitride layer can account for 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% of the total thickness of the nickel-containing electrode.

[0064] In some implementations, such as Figure 1 As shown, the thickness of the nickel-containing nitride layer refers to... Figure 1 The sum of d1 and d2 shown.

[0065] In this application, the thickness of the nickel-containing nitride layer can provide a larger contact area for the reaction.

[0066] In this application, the thickness of the nickel-containing nitride layer can be determined using conventional methods in the art, such as by combining scanning electron microscope images of the transverse or longitudinal sections of the electrode unit skeleton with EDS elemental analysis.

[0067] In some embodiments, the molar content of nitrogen in the region between the nickel-containing metal layer and the nickel-containing nitride layer is 10-30%, preferably 12-22%, and more preferably 12-15%.

[0068] For example, the molar content of nitrogen in the region between the nickel-containing nitride layer region near the nickel-containing metal layer and the nickel-containing nitride layer surface region far from the nickel-containing metal layer can be 10%, 15%, 20%, 25%, 30%, etc.

[0069] In this application, the molar content of nitrogen can be determined according to the method described above.

[0070] The molar content of nitrogen refers to the molar content of nitrogen relative to all elements within the detection area.

[0071] In this application, the nickel-containing nitride layer region near the nickel-containing metal layer and the nickel-containing nitride layer surface region far from the nickel-containing metal layer are defined as above.

[0072] In some embodiments, the nickel-containing nitride layer comprises Ni3N, unsaturated nickel nitride, and metallic nickel. In some embodiments, the nickel-containing nitride layer further comprises Ni4N.

[0073] In this application, no restrictions are placed on the determination of the material types of Ni3N, Ni4N, unsaturated nickel nitride, and metallic nickel in the nitride layer. The selection can be made as needed. For example, X-ray diffraction (XRD) can be used to obtain diffraction peak information of the crystalline material, and then the lattice fringes of different components in the obtained sample can be observed by high-resolution transmission electron microscopy (HR-TEM) to determine the material type.

[0074] The nickel-containing nitride layer of this application contains the substances described above, which can ensure the generation of defect sites and the realization of high activity.

[0075] In this application, the unsaturated nickel nitride refers to nickel nitride with nitrogen defects, where the nitrogen defect refers to a difference in the bonding form between Ni and N compared to intrinsic nickel nitride. In this application, the sample's X-ray photoelectron spectroscopy (XPS, calibrated with a C1s peak at 284.8 eV) shows Ni 2p 3 / 2 The peak at 852-853 eV in the region is attributed to nickel atom sites at surrounding nitrogen-containing defect sites, and the peak area of ​​this peak accounts for a significant portion of the total Ni 2p2 eV. 3 / 2 The ratio of peak areas is denoted as n. x n x The content is 20-60%, preferably 25-50%, and more preferably 30-40%.

[0076] For example, the n x It can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0077] Due to the n in nickel-containing electrodes x A higher value indicates a higher nitrogen defect content in the nickel-containing electrode, thus giving the nickel-containing electrode higher chemical stability.

[0078] In this application, both the nickel metal unit cell and the Ni4N crystal unit cell are face-centered cubic, and the lattice constant of nickel is... The lattice constant of Ni4N is With a low degree of nitriding, the nickel lattice can gradually transform into a Ni4N lattice; as the number of interstitial nitrogen atoms decreases, the Ni4N lattice can also gradually transition to a metallic nickel lattice. With a low degree of nitriding, no additional large line or planar defects are generated in a single nickel crystal, and no additional grain boundaries are formed, thus minimizing the electron transport resistance between nickel and nickel nitride and ensuring the overall stability of the electrode structure. The distribution of nickel and nickel nitride layers on the electrode cross-section can be observed and determined using confocal ion beam scanning electron microscopy (FIB-SEM), and the degree of lattice distortion of different nickel grains can be observed using grazing incidence wide-angle X-ray scattering (GIWAXS).

[0079] The lattice parameters of Ni3N differ significantly from those of nickel metal (as mentioned above, the lattice constant of Ni metal is...). The lattice constant of Ni3N The presence of a small amount of intrinsic Ni3N crystals can easily lead to the formation of more unstable crystal interfaces, and may even form particles that detach from the electrode. Therefore, it is undesirable to form too many intrinsic Ni3N crystals. The presence of a small amount of thin Ni3N will ensure the formation of highly catalytically active nitrogen defect sites.

[0080] In some embodiments, the nickel-containing nitride layer has a molar content of 50-100% relative to all metal elements; preferably, when the molar content of nickel in the nickel-containing nitride layer is less than 100%, the nickel-containing nitride layer also contains other metals, preferably selected from one or more of molybdenum, copper, cobalt, iron, tungsten, and ruthenium.

[0081] In this application, "other metals" refers to metals other than nickel.

[0082] For example, in the nickel-containing nitride layer, the molar content of nickel relative to all metal elements can be 50%, 60%, 70%, 80%, 90%, 100%, etc.

[0083] In this application, no restrictions are placed on the determination of the molar content of nickel; it can be determined using methods conventional in the art, such as energy dispersive spectroscopy (EDS). In some embodiments, analysis by confocal ion beam scanning electron microscopy (FIB-SEM) revealed that 50-95% of the nickel crystals at the interface region between the nickel-containing nitride layer and the nickel-containing metal layer are shared by the nickel-containing nitride layer and the nickel-containing metal layer.

[0084] like Figure 1 As shown, 50-95% of the nickel crystals on the interface region between the nickel-containing nitride layer 2 and the nickel-containing metal layer 1 are shared by the nickel-containing nitride layer 2 and the nickel-containing metal layer 1.

[0085] In some embodiments, the lattice distortion of a single nickel crystal shared by the nickel-containing nitride layer and the nickel-containing metal layer is less than 15%.

[0086] In this application, the lattice distortion refers to Δd / d, where d is the normal lattice spacing of a crystal, and Δd is the difference between the normal lattice spacing and the lattice spacing of the distorted region.

[0087] In this application, the nickel-containing nitride layer is the catalytic active layer in the nickel-containing electrode. Its surface has abundant open pores, which can increase the catalytic reaction area. Its surface is rich in nitrogen defect sites with hydrogen production activity close to that of the noble metal platinum, which can effectively improve the electrolysis efficiency of the electrode and the electro-chemical energy conversion efficiency. The structure of the nitride layer itself and the interface structure with the nickel-containing metal layer are relatively stable, which can ensure the overall structural stability of the electrode.

[0088] In some embodiments, the thickness of the nickel-containing metal layer accounts for 50-90% of the thickness of the nickel-containing electrode, preferably 50-80%, and more preferably 60-70%.

[0089] like Figure 1 As shown, L is the thickness of the nickel-containing metal layer.

[0090] For example, the thickness of the nickel-containing metal layer accounts for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% of the thickness of the nickel-containing electrode.

[0091] In this application, no restrictions are placed on the method for measuring the thickness of the nickel-containing metal layer. It can be measured in accordance with conventional methods in the art, such as using a scanning electron microscope.

[0092] In some embodiments, the porosity of the nickel-containing metal layer is less than 5%, preferably less than 2%, making the nickel-containing metal layer structure dense.

[0093] In some embodiments, the nickel-containing metal layer is nickel or contains elemental metals other than nickel. Preferably, the elemental metals other than nickel are selected from one or more of molybdenum, vanadium, iron, cobalt, copper, tungsten, and ruthenium.

[0094] The nickel-containing metal layer of this application, by including elemental metals other than nickel, can increase the number of catalytically active sites on the material surface and optimize the distribution of electronic state density within electrode atoms, thereby giving it higher charge conductivity and catalytic activity.

[0095] In some embodiments, the impurity content of the nickel-containing metal layer is less than 2%, preferably less than 1%.

[0096] In some embodiments, the nitrogen content in the nickel-containing metal layer is less than 0.1%.

[0097] The nickel-containing metal layer is the main skeleton of the nickel-containing electrode. Due to its low impurity and nitrogen content, it has good mechanical strength and conductivity.

[0098] In some embodiments, the thickness of the nickel-containing electrode is 200 μm-2 mm, preferably 300 μm-1 mm.

[0099] For example, the thickness of the nickel-containing electrode can be 200μm, 500μm, 1mm, 1.5mm, 2mm, etc.

[0100] This application sets the thickness of the nickel-containing electrode within the above-mentioned range, which can ensure the effective diffusion of gas-liquid reactants and products during the use of the nickel-containing electrode. If the nickel-containing electrode is too thick, the gas cannot diffuse out quickly from the gaps in the nickel-containing electrode, which hinders the contact between the electrolyte and the electrode surface, thereby increasing the system resistance.

[0101] In some embodiments, the nickel-containing electrode is in the form of a wire mesh, a porous plate mesh, or a foam. In some embodiments, the nickel-containing electrode is in the form of a wire mesh, and the diameter of the nickel-containing electrode is 200-500 μm, preferably 250-450 μm, and more preferably 300-400 μm.

[0102] For example, the diameter of the nickel-containing electrode can be 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, etc.

[0103] This application sets the diameter of the nickel-containing electrode within the specified range to ensure sufficient mechanical strength, mechanical stability, and specific surface area. If the diameter of the nickel-containing electrode is too small, it is prone to breakage during use, which affects the working efficiency of the electrode. If the diameter of the nickel-containing electrode is too large, the surface area corresponding to the unit electrode mass is small, and the utilization rate of the nickel-containing electrode is low.

[0104] The nickel-containing electrode described in this application has a high contact surface area, abundant catalytic active sites, and higher stability, and it operates at 100 mA / cm². 2 The overpotential change was small after 100 hours of operation, indicating that the nickel-containing electrode has good stability.

[0105] This application provides a method for preparing a nickel-containing electrode, comprising:

[0106] (1) Provide nickel-containing framework network materials;

[0107] (2) The surface layer of the nickel-containing framework network material is converted in situ into a nickel-containing nitride layer to obtain a nickel-containing framework network material with a nickel-containing nitride layer on the surface.

[0108] (3) The nickel-containing nitride layer is partially decomposed to form a porous structure to obtain a nickel-containing electrode.

[0109] In this application, no restrictions are placed on the nickel-containing framework network material, as long as it is a three-dimensional material. For example, the nickel-containing framework network material can be a metal wire mesh, a porous plate mesh, a metal foam, or other framework network structures. In some embodiments, the nickel-containing framework network material may contain other elemental metals besides nickel, such as copper, iron, vanadium, molybdenum, cobalt, tungsten, etc. In some embodiments, the nickel-containing metal network material can be a homogeneous structure or a multilayer heterogeneous structure connected by metallic bonds. No restrictions are placed on the surface flatness of the nickel-containing framework network material; it can be conventionally selected as needed.

[0110] This application does not impose any restrictions on the size of the nickel-containing framework network material, as long as it can be fabricated into the nickel-containing electrode described above.

[0111] In some embodiments, in step (1), acidic hydrogen peroxide, alkali (such as sodium hydroxide, potassium hydroxide, etc.), acid (such as sulfuric acid, hydrochloric acid, nitric acid, etc.) and / or organic solvents (such as acetone, ethanol, isopropanol, etc.) are used to remove organic matter and oxide layer from the surface of the nickel-containing skeleton network material.

[0112] In this application, the method for in-situ conversion of the surface layer of a nickel-containing backbone network material into a nickel-containing nitride layer to obtain a nickel-containing backbone network material with a nickel-containing nitride layer is not limited in any way, and can be selected as needed. For example, an ammonia atmosphere nitriding or ion nitriding method can be used. In some embodiments, the ammonia atmosphere in the ammonia atmosphere nitriding can be generated by a substance containing amino groups. Preferably, the substance containing amino groups can be ammonia, hydrazine, urea, dicyandiamide, or melamine. In some embodiments, the ion nitriding can be plasma nitriding. Preferably, the plasma source for plasma nitriding can be a nitrogen-containing gas, such as nitrogen, ammonia, or hydrazine. For example, the plasma source can contain nitrogen, ammonia, or hydrazine. In some embodiments, the gas in ammonia atmosphere nitriding and ion nitriding can also contain inert gases and / or reducing gases, such as nitrogen, argon, helium, and / or hydrogen. In some embodiments, the ammonia or nitrogen plasma content in the ammonia atmosphere nitriding or ion nitriding accounts for 10-99% of the total atmosphere material, preferably 20-90%, and more preferably 30-80%.

[0113] In some embodiments, the surface layer of the nickel-containing framework network material is in-situ converted into a nickel-containing nitride layer under ammonia nitriding or ion nitriding conditions to obtain a nickel-containing framework network material with a nickel-containing nitride layer on the surface. In some embodiments, the reaction temperature is below 400°C, preferably 350-400°C, and more preferably 350-380°C;

[0114] Preferably, the reaction time is 0.1-24h, more preferably 0.1-12h, and even more preferably 0.1-5h.

[0115] When nickel-containing framework network materials are reacted under ammonia atmosphere nitriding or ion nitriding conditions, the metal on the surface of the nickel-containing framework network material will be nitrided layer by layer to form a gradient nitriding layer, with the degree of nitriding gradually decreasing from the surface to the inside.

[0116] In some embodiments, the temperature at which the nickel-containing nitride layer partially decomposes is above 400°C, preferably 450-850°C, and more preferably 550-650°C;

[0117] Preferably, the decomposition time of the nickel-containing nitride layer is 0.1-48h, more preferably 0.5-24h, and even more preferably 0.5-12h.

[0118] Because the nickel-containing nitride layer contains metallic nitrides such as nickel nitride, copper nitride, and iron nitride, and these metallic nitrides are unstable above 400°C, the nickel-containing nitride layer partially decomposes to form nitrogen defects and metallic elements or alloys. The released nitrogen creates pores on the electrode surface. At the same time, some nitrogen in the crystal lattice may move to the unnitrided nickel-containing metal layer region due to the increased atomic kinetic energy, thus increasing the depth of the nitride layer.

[0119] In some embodiments, the atmosphere in which the nickel-containing nitride layer decomposes may be the same as or different from the atmosphere in which the nickel-containing framework network material with the nickel-containing nitride layer on its surface is formed. Preferably, the ammonia or nitrogen plasma content in the atmosphere in which the nickel-containing nitride layer decomposes is lower than the ammonia or nitrogen plasma content in the atmosphere in which the nickel-containing framework network material with the nickel-containing nitride layer on its surface is formed. Preferably, the ammonia or nitrogen plasma content is 10-80%, more preferably 10-60%, and even more preferably 10-30%. The atmosphere may also contain an inert gas and / or a reducing gas, such as nitrogen, argon, helium, and / or hydrogen.

[0120] In some implementations, steps (2) and (3) are repeated 1-20 times, preferably 2-15 times, and more preferably 5-10 times.

[0121] Repeating steps (2) and (3) can yield richer voids and a deeper nitride layer thickness. Preferably, after repeating steps (2) and (3), the nickel-containing electrode can be obtained by cooling in an inert atmosphere.

[0122] In this application, the reaction parameters can be changed as needed for repeating steps (2) and (3). That is, the reaction parameters in step (2) can be different from those in step (2) when repeating step (2).

[0123] This application makes no restrictions on the inert atmosphere, which can be selected as needed, such as one or more of nitrogen, argon, and helium.

[0124] In some embodiments, in step (2), one side of the nickel-containing skeleton network material is converted in situ into a nickel-containing nitride layer, while the other side is not nitrided.

[0125] This application provides a nickel-containing electrode, which is prepared according to the method described above.

[0126] In some embodiments, the nickel-containing electrode is the nickel-containing electrode described above.

[0127] This application provides the application of the nickel-containing electrode described above or the nickel-containing electrode prepared by the method described above in the field of catalysis.

[0128] In some embodiments, the nickel-containing electrode is used for reactions that catalyze hydrogen evolution, oxygen evolution, hydrogen oxidation, or oxygen reduction.

[0129] In this application, the applications in the fields of catalysis and / or electrochemistry include hydrogen production by water electrolysis, oxygen production, electrocatalytic oxidation of organic matter, electrocatalytic hydrogen oxidation in fuel cells, negative electrodes of metal-ion batteries, supercapacitors, and hydrogen production by catalytic hydrolysis of hydrogen-containing compounds.

[0130] This application provides an electrochemical battery comprising the nickel-containing electrode described above or the nickel-containing electrode prepared by the method described above.

[0131] In this application, the electrochemical cell may include an electrolyzer, a chlor-alkali cell, an organic degradation cell, a fuel cell, a metal-ion cell, a supercapacitor, and / or a catalytic hydrolysis device, etc.

[0132] Example

[0133] This application provides a general and / or specific description of the materials and methods used in the experiments. Unless otherwise specified, all reagents and instruments used are commercially available products.

[0134] Example 1: Preparation of Nickel-Containing Electrode

[0135] (1) Select an area of ​​5×5cm 2 A nickel wire mesh with a mesh size of 50 and a wire diameter of 250μm was used as the nickel-containing skeleton network material. The surface of the nickel-containing skeleton network material was cleaned with acetone, ethanol and dilute sulfuric acid to remove surface organic matter and oxide layer.

[0136] (2) The nickel-containing skeleton network material is placed in the front section of a three-stage reactor with 50% ammonia / nitrogen gas. After ensuring that there are no impurities, the reactor is heated to 360°C. The reaction is carried out for 30 minutes with a gas flow rate of 5 ml / min to obtain a nickel-containing skeleton network material with a nickel nitride layer on the surface.

[0137] (3) Transfer the nickel-containing skeleton network material with a nickel-containing nitride layer on the surface to the middle section of the reactor at a temperature of 600°C and a constant reaction atmosphere for 20 min.

[0138] (4) Repeat steps (2) and (3) 6 times. The reaction time of the last step (3) is 10 min. Then transfer to the room temperature section at the end of the reactor and cool in a nitrogen atmosphere with a nitrogen flow rate of 10 mL / min to obtain a nickel-containing electrode.

[0139] The resulting nickel-containing electrode has an overall wire mesh structure with a wire diameter of 270 μm (i.e., a total thickness of 270 μm) and a mesh size of 50. The skeleton units are composed of cylindrical shapes (e.g., ...). Figure 1 (As shown). X-ray energy-dispersive X-ray spectroscopy (EDS) was performed on the cross-section of the cylinder using a scanning electron microscope (this method can determine the elemental content and distribution on the cross-section). The first surface layer near the center, with an average nitrogen content of 0.1%, was selected as the boundary between the nickel-containing metal layer 1 and the nickel-containing nitride layer 2. The diameter of the nickel-containing metal layer 1 is approximately 180 μm, accounting for 66.6% of the total thickness of the nickel-containing electrode. The nickel-containing metal layer 1 is a solid structure with a porosity close to 0. The thickness of the nickel-containing nitride layer (referring to the sum of the thicknesses of the upper and lower nitride layers shown in the longitudinal section) is 90 μm, accounting for 33.3% of the total thickness. From the cross-section, the thickness of the nickel-containing nitride layer is 45 μm. High-resolution scanning electron microscopy observation of the surface image of the nickel-containing nitride layer estimated the porosity to be 52-55% and the average opening size to be 5 μm. EDS scanning (a characterization method with a detection depth of approximately 10 nm) of the nickel-containing electrode surface revealed a nitrogen molar content of approximately 15-17%. X-ray energy dispersive spectroscopy (XPS, with a detection depth of 1-2 nm) scanning of the bulk sample surface, along with XPS analysis, showed that Ni 2p... 3 / 2 The peak located at 852-853 eV in the region accounts for a portion of Ni 2p. 3 / 2 The ratio of peak areas n x The porosity was estimated to be 39-41%. After etching to a depth of 10 μm, the surface porosity was reduced to 35-40%, and the molar nitrogen content measured by EDS increased to 19%. When the etching depth reached 35 μm, the porosity was less than 5%, and the molar nitrogen content measured by EDS was 8-10%. X-ray diffraction analysis detected elemental nickel and weak Ni4N and Ni3N lattice diffraction peaks.

[0140] Example 2: Preparation of Nickel-Containing Electrode

[0141] Example 2's electrode structure, microstructure, and synthesis are similar to Example 1. The difference between Example 2 and Example 1 is that the electrode in Example 2 has a rhomboid cross-section. Figure 2 As shown.

[0142] Example 3: Preparation of Nickel-Containing Electrode

[0143] (1) Select an area of ​​5×5cm 2 Nickel foam with a porosity of 50% and a wire diameter of 280μm was used as a nickel-containing skeleton network material. It was cleaned with ethanol, acetone and water respectively to remove surface organic matter. Then, acidic hydrogen peroxide (H2SO4:H2O2=4:1) was used to clean the surface of the nickel-containing skeleton network material to remove the surface oxide layer.

[0144] (2) The nickel-containing framework network material was placed in a first reactor with 20% hydrazine hydrate / nitrogen gas. After ensuring that there were no impurities, the reactor was heated to 350°C. The reaction was carried out for 40 minutes with a gas flow rate of 3 ml / min to obtain a nickel-containing framework network material with a nitride layer on the surface.

[0145] (3) Transfer the nickel-containing skeleton network material with nitride layer on the surface to the second reactor, maintain the reaction temperature at 650℃, the reaction atmosphere at 10% ammonia / 5% H2 / Ar, the gas flow rate at 5ml / min, and the reaction time at 20min.

[0146] (4) Repeat steps (2) for 30 min, (3) for 20 min, (2) for 20 min, (3) for 10 min, (2) for 10 min, and (3) at 600℃ for 10 min. Then transfer to the final section of the reactor at room temperature and cool in a nitrogen atmosphere with a nitrogen flow rate of 10 mL / min to obtain a nickel-containing electrode.

[0147] The nickel-containing electrode has an overall structure similar to nickel foam, but its framework diameter is about 300 μm, approximately three times larger than that of commonly used nickel foam (about 100 μm). The overall porosity of the nickel-containing electrode is approximately 50%. Figure 1 As shown, the first surface layer near the center with an average nitrogen content of 0.1% serves as the boundary between the nickel-containing metal layer 1 and the nitride layer 2. In Example 3, the longest diameter of the nickel layer at the center of the electrode skeleton is approximately 200 μm. The nickel layer has a solid structure with a porosity close to 0, and the nickel purity in the nitrogen-free region reaches 99.9%. The thickness of the nickel nitride layer in cross-section is approximately 50 μm. High-resolution scanning electron microscopy (SEM) images of the nitride layer surface suggest a porosity of 58-60% and an average opening size of 6 μm. EDS analysis indicates that the molar nitrogen content on the electrode surface is approximately 12-13%. XPS energy dispersive spectroscopy analysis shows that Ni 2p 3 / 2The peak located at 852-853 eV in the region accounts for a portion of Ni 2p. 3 / 2 The ratio of peak areas n x The porosity was estimated to be 48-50%. After etching to a depth of 10 μm, the surface porosity was estimated to decrease to about 45%, and the EDS nitrogen content increased to about 16%. When the etching depth reached 40 μm, the porosity was less than 5%, and the EDS nitrogen content was less than 5%. X-ray diffraction analysis detected elemental nickel and weak Ni4N and Ni3N lattice diffraction peaks.

[0148] Example 4: Preparation of Nickel-Containing Electrode

[0149] The preparation method is the same as in Example 1, except that the repeat conditions for steps (2) and (3) are: step (2) 30 min, step (3) 30 min, step (2) 30 min, step (3) 20 min, step (2) 30 min, step (3) 10 min, and step (2) 5 min.

[0150] The overall structure of the obtained nickel-containing electrode is similar to that of Example 1. Microstructurally, Example 4 showed a higher molar nitrogen content (18-20%) on the surface, as measured by EDS; the porosity was also lower, at 40-45%. XPS energy dispersive spectroscopy analysis showed that Ni 2p... 3 / 2 The peak located at 852-853 eV in the region accounts for a portion of Ni 2p. 3 / 2 The ratio of peak areas n x It is 40-42%.

[0151] Example 5: Preparation of Nickel-Containing Electrode

[0152] The preparation method is the same as in Example 1, except that steps (2) and (3) are repeated 4 times, with the following conditions: step (2) 45 min, step (3) 30 min, step (2) 20 min, and step (3) 10 min.

[0153] The overall structure of the obtained nickel-containing electrode is similar to that of Example 1. In terms of microstructure, the nickel-containing nitride layer of Example 5 is thinner, about 38 μm; the surface nitrogen content measured by EDS is 10-12%.

[0154] Example 6: Preparation of Nickel-Containing Electrode

[0155] The preparation methods of Example 6 and Example 1 are the same, except that the ammonia atmosphere in the first step (2) is achieved by embedding the nickel-containing skeleton network material into urea powder and protecting it with an argon atmosphere. The reactor is sealed and heated to 330°C for 40 min. In step (3), the atmosphere is pure argon, 600°C, and the reaction is carried out for 20 min. Finally, under the same conditions, 30% ammonia / 5% hydrogen / Ar gas is passed through at a flow rate of 5 ml / min, and the reactor is slowly cooled to room temperature at a time of 3°C / min to obtain the nickel-containing electrode.

[0156] The overall structure of the obtained nickel-containing electrode is similar to that of Example 1, but the nickel-containing electrode skeleton in Example 6 has a larger diameter, approximately 350 μm, and the diameter of the nickel-containing metal layer is approximately 250 μm, with a porosity of approximately 2%. The nickel-containing nitride layer has a thickness of approximately 50 μm, a surface porosity of 51-55%, and an average opening size of 5 μm. EDS analysis showed that the molar content of nitrogen in the surface layer of the nickel-containing nitride layer was 15-17%, and XPS energy dispersive spectroscopy analysis showed that Ni 2p 3 / 2 The peak located at 852-853 eV in the region accounts for a portion of Ni 2p. 3 / 2 The ratio of peak areas n x It is 47-49%.

[0157] Table 1. Parameters of the nickel-containing electrodes obtained in Examples 1-6

[0158]

[0159] Comparative Example 1

[0160] Commercially available nickel foam electrodes with 30 pores per inch, a thickness of 1 mm, and a skeleton diameter of approximately 100 μm.

[0161] Comparative Example 2

[0162] Ni3N-containing surface layer prepared according to the nitrogen microwave plasma bombardment method disclosed by Bin Liu et al. 1-x The granular layer of nickel foam electrode (Bin Liu et al., Unconventional Nickel Nitride Enriched with Nitrogen Vacancies as a High-Efficiency Electrocatalyst for Hydrogen Evolution, doi:10.1002 / advs.201800406). The main steps are: to form a 5×5cm area... 2 Thickness 0.5mm, porosity 96%, pore size 0.25-0.3mm, areal density 310g / cm³ 2After being cleaned with acetone, ethanol, and water, the foamed nickel was placed in a microwave plasma vapor deposition reactor. The microwave power was 450W, the pressure was 14 Torr, the nitrogen flow rate was 30 ml / min, the electrode surface temperature was 300℃, and the electrode surface was bombarded with plasma for 90 seconds. After natural cooling to room temperature, the surface layer contained Ni3N. 1-x A foamed nickel electrode with a granular layer, the electrode surface containing a nickel nitride granular layer of approximately 1 μm, and the sample surface XPS analysis showed n... x The value is approximately 27%.

[0163] Experimental Example

[0164] 5*5cm 2 The electrodes prepared in the above embodiments and comparative examples were used as working electrodes and tested in a three-electrode system. The electrolyte was 1M KOH, the counter electrode was a nickel mesh, and the reference electrode was a Hg / HgO electrode. The different electrodes were tested according to conventional methods at current densities of 10 and 100 mA / cm². 2 Overpotential at 100 mA / cm 2 The variation of overpotential values ​​after 100 hours of operation at current density is shown in Table 2.

[0165] Table 2 Overpotential table for different electrodes

[0166]

[0167] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the protection scope of this application.

Claims

1. A nickel-containing electrode, wherein, The nickel-containing electrode comprises a nickel-containing metal layer and a nickel-containing nitride layer from the inside out. The molar content of nitrogen in the nickel-containing nitride layer first increases and then decreases from the inside out along the direction away from the nickel-containing metal layer. The nickel-containing nitride layer has open pores, and its porosity gradually increases along the direction away from the nickel-containing metal layer; The nickel-containing nitride layer comprises Ni3N, unsaturated nickel nitride, metallic nickel, and Ni4N; The porosity of the nickel nitride layer surface region, far from the nickel-containing metal layer, is 40-70%. The nickel-containing metal layer is nickel or contains elemental metals other than nickel, wherein the elemental metals other than nickel are selected from one or more of molybdenum, vanadium, iron, cobalt, copper, tungsten and ruthenium.

2. The nickel-containing electrode according to claim 1, wherein, The total thickness of the nickel-containing nitride layer accounts for 10-50% of the total thickness of the nickel-containing electrode.

3. The nickel-containing electrode according to claim 1, wherein, The molar content of nitrogen in the region between the nickel-containing nitride layer region near the nickel-containing metal layer and the nickel-containing nitride layer surface region far from the nickel-containing metal layer is 10-30%.

4. The nickel-containing electrode according to claim 1, wherein, In the nickel-containing nitride layer, the molar content of nickel relative to all metal elements is 50-100%; wherein, when the molar content of nickel in the nickel-containing nitride layer is less than 100%, the nickel-containing nitride layer also includes other metals, which are selected from one or more of molybdenum, copper, cobalt, iron, tungsten and ruthenium.

5. The nickel-containing electrode according to any one of claims 1-4, wherein, The thickness of the nickel-containing metal layer accounts for 50-90% of the thickness of the nickel-containing electrode.

6. The nickel-containing electrode according to any one of claims 1-4, wherein, The porosity of the nickel-containing metal layer is less than 5%.

7. The nickel-containing electrode according to any one of claims 1-4, wherein, The thickness of the nickel-containing electrode is 200 μm-2 mm.

8. The nickel-containing electrode according to any one of claims 1-4, wherein, The nickel-containing electrode is in the form of a wire mesh, a porous plate mesh, or a foam.

9. The nickel-containing electrode according to claim 8, wherein, The nickel-containing electrode is in the form of a wire mesh, and the diameter of the nickel-containing electrode is 200-500 μm.

10. A method for preparing a nickel-containing electrode, comprising: (1) Provide nickel-containing framework network materials; (2) The surface layer of the nickel-containing framework network material is converted in situ into a nickel-containing nitride layer to obtain a nickel-containing framework network material with a nickel-containing nitride layer on the surface; (3) The nickel-containing nitride layer is partially decomposed to form a porous structure to obtain a nickel-containing electrode; In step (3), the decomposition temperature of the nickel-containing nitride layer on the surface to form a porous structure is above 400°C.

11. The method of claim 10, wherein The decomposition time is 0.1-45 hours.

12. The method according to claim 10, wherein, In step (2), the surface layer of the nickel-containing skeleton network material is nitrided in an ammonia atmosphere or ion nitrided to obtain a nickel-containing skeleton network material with a nickel metal nitride layer on the surface.

13. The method according to claim 12, wherein, In the ammonia atmosphere nitriding process, the ammonia atmosphere is generated by an amino-containing substance.

14. The method according to claim 12, wherein, The nitrogen plasma source in the ion nitridation contains nitrogen, ammonia, or hydrazine.

15. The method according to claim 12, wherein, Steps (2) and (3) are repeated 1-20 times.

16. The method according to claim 12, wherein, In step (2), one side of the nickel-containing skeleton network material is converted in situ into a nickel-containing nitride layer, while the other side is not nitrided.

17. The application of the nickel-containing electrode according to any one of claims 1-9 in the field of catalysis.

18. In the application according to claim 17, the nickel-containing electrode is used for catalytic hydrogen evolution, catalytic oxygen evolution, catalytic hydrogen oxidation, or catalytic oxygen reduction reactions.

19. An electrochemical cell comprising a nickel-containing electrode according to any one of claims 1-9.

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