A method for preparing an electrode material by magnetic field-induced ion substitution and an electrode material

Abstract

The application discloses a method for preparing electrode materials by magnetic field-induced ion replacement and electrode materials, and belongs to the technical field of functional material preparation. The method comprises the following steps: loading a cobalt-containing metal organic framework material on the surface of a nickel base material through a self-assembly process, and then placing the loaded composite material in a multi-metal mixed salt solution to perform an ion replacement reaction under the driving of an external magnetic field. The method activates the soft magnetic characteristics of the base material by using a magnetic field, can overcome the steric hindrance and high replacement energy barrier caused by the large difference in ion radius, and can thus realize efficient replacement at normal temperature and pressure, form unique active sites and pore structures, and adjust the electronic properties and charge distribution of the material through the strain effect induced by the difference in ion radius, so that the oxygen evolution activity and stability are optimized. The method does not require complex equipment and harsh conditions, is controllable and simple in operation, has the potential for large-scale preparation, and provides a feasible scheme for reducing the cost and increasing the efficiency of an alkaline electrolytic cell.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional material preparation, and particularly relates to a method for preparing an electrode material through magnetic field-induced ion replacement and the electrode material. BACKGROUND

[0002] As a green and sustainable energy conversion approach, electrocatalytic water splitting for hydrogen production has attracted much attention due to its ability to convert renewable energy (such as solar energy and wind energy) into high-energy-density hydrogen energy. However, the electrocatalytic oxygen evolution reaction (OER) as the anodic half-reaction of water splitting involves a complex four-electron transfer process, which is slow in kinetics and has a high overpotential, both of which will restrict the overall energy conversion efficiency. Therefore, developing an efficient, stable, and low-cost oxygen evolution electrode is of great significance to improve the performance of alkaline electrolyzers.

[0003] At present, noble metal-based materials such as IrO2 and RuO2 are known to have excellent performance as oxygen evolution reaction catalysts, but their limited reserves and high prices greatly limit their application in large-scale industrial production. Transition metal-based materials have empty d electron orbitals and adjustable electronic structures, and exhibit good catalytic activity and stability in the oxygen evolution reaction, making them ideal candidates to replace noble metal-based materials. Compared with single-element transition metal materials, multi-element transition metal materials can effectively optimize the electronic structure and surface chemical properties of the material through the synergistic effect between different components, thereby often exhibiting more excellent catalytic performance. Ion replacement method can introduce target ions into the framework structure or interstitial position of the material, which can realize the regulation of the performance of the catalytic material, and has the advantages of mild operation, strong controllability and high engineering feasibility. Generally, when the size difference between the replacement ion and the original ion of the host material is small, the reaction can be self-driven; but when the size difference is large, the replacement can only be achieved under strong driving conditions such as high temperature and high pressure, which is not conducive to the large-scale preparation of oxygen evolution active materials.

[0004] Therefore, it is urgent to develop a mild and low-cost ion replacement induction method for the preparation of oxygen evolution active materials. SUMMARY

[0005] The purpose of the present application is to provide a method for preparing an electrode material through magnetic field-induced ion replacement and the electrode material, which can effectively solve the problems of low replacement efficiency, difficulty in doping and alloying caused by large ion replacement potential barrier, and can effectively regulate the micro-morphology and chemical distribution of the catalyst to obtain an electrode material containing a high-efficiency and stable catalyst.

[0006] To achieve the above purpose, the present application provides a method for preparing an electrode material through magnetic field-induced ion replacement, comprising the following steps:

[0007] The nickel-based material is pre-impregnated by using a ligand aqueous solution to obtain a pretreated nickel-based material; the pretreated nickel-based material is repeatedly impregnated by using a cobalt salt solution and a ligand aqueous solution in sequence to obtain a composite material;

[0008] The mixed solution of the A salt solution and the B salt solution is configured as an ion replacement solution, and the composite material is subjected to an ion replacement reaction by using the ion replacement solution under the action of an applied magnetic field to obtain an electrode material.

[0009] The A salt solution includes at least one of a molybdenum salt solution, a nickel salt solution and an iron salt solution, and the B salt solution includes at least one of a manganese salt solution, a cerium salt solution and a lanthanum salt solution.

[0010] Further, the concentration of the cobalt salt solution is 0.1M-1.0M, and the cobalt salt solution includes at least one of CoCl2 solution, CoSO4 solution, Co(NO3)2 solution, Co(CH3COO)2·4H2O solution and CoC2O4 solution.

[0011] Further, the concentration of the ligand aqueous solution is 0.5M-3.0M, and the ligand aqueous solution includes at least one of terephthalic acid solution, 2-nitroimidazole solution, 2-methylimidazole solution, benzimidazole solution and 2-chloroimidazole solution.

[0012] Further, in the pre-impregnation process, the impregnation temperature is 40℃-70℃, and the impregnation time is 20min-40min.

[0013] Further, in the impregnation process, the impregnation temperature of the pretreated nickel-based material in the cobalt salt solution is room temperature, and the impregnation time is 5min-10min; the impregnation temperature of the pretreated nickel-based material in the ligand aqueous solution is 40℃-70℃, and the impregnation time is 20min-40min; wherein the loading amount of the composite material is not less than 5mg / cm 2 .

[0014] Further, the concentration of the A salt solution or the B salt solution is 0.01M-1M.

[0015] Further, the molybdenum salt solution includes at least one of Na2MoO4 solution, (NH4)6Mo7O 24 solution, Mo(C5H7O2)3 solution and (C5H5)2MoCl2 solution, the nickel salt solution includes at least one of NiCl2 solution, NiSO4 solution, Ni(NO3)2 solution, Ni(CH3COO)2 solution and NiC2O4 solution, and the iron salt solution includes at least one of FeCl2 solution, FeSO4 solution, Fe(NO3)3 solution, FeC6H5O7 solution and Fe2(C2O4)3 solution.

[0016] Further, the manganese salt solution includes at least one of MnCl2 solution, Mn(NO3)2 solution, MnSO4 solution and Mn3(C6H5O7)2 solution, the cerium salt includes at least one of Ce2(SO4)3 solution, CeCl3 solution, Ce(NO3)3 solution, Ce(C6H5O7) solution and Ce(C5H7O2)3 solution, and the lanthanum salt includes at least one of La2(SO4)3 solution, LaCl3 solution, La(NO3)3 solution, La(C5H7O2)3 solution and La(C6H5O7) solution.

[0017] Further, the strength of the applied magnetic field is 0.1T-0.8T, the reaction temperature of the ion substitution reaction is 20°C-60°C, and the reaction time is 3h-6h.

[0018] The application also provides an electrode material obtained by the above method.

[0019] In summary, the application has the following advantages:

[0020] The application provides a method for preparing an electrode material by magnetic field-induced ion substitution. For the substitution process of elements with a significant difference in ionic radius from the host atoms, the method realizes controllable ion substitution by applying an external magnetic field. The specific principle is as follows: the ion migration and substitution path is regulated by the Lorentz force effect and magnetic orientation effect, effectively reducing the ion substitution barrier, solving the problems of low substitution efficiency, difficulty in realizing element doping and alloying caused by high barrier in traditional processes. At the same time, the method can simultaneously regulate the micro-morphology and element chemical distribution of the oxygen evolution catalyst, realize the regulation of the electronic valence state of the oxygen evolution reaction active site, and thus optimize the catalytic activity and stability of the prepared oxygen evolution electrode, so that both are optimized. The method not only has simple process and strong regulation, but also provides a new technical idea for the large-scale preparation of high-performance electrocatalysts, and has important application prospects in the industrialized production field of efficient oxygen evolution active materials. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A schematic diagram of a device for preparing an electrode material by magnetic field-induced ion substitution according to an embodiment of the application;

[0022] Figure 2 A schematic diagram of the appearance of the NF / ZIF-67@NiCe (magnetic) material prepared in Example 1;

[0023] Figure 3 A micro-morphology diagram of the NF / ZIF-67@NiCe (magnetic) material prepared in Example 1;

[0024] Figure 4 An XRD diagram of the NF / ZIF-67@NiCe (magnetic) material prepared in Example 1;

[0025] Figure 5 XPS image of the NF / ZIF-67@NiCe (magnetized) material prepared in Example 1;

[0026] Figure 6 A comparison graph showing the electrochemical performance of the materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0027] Figure 7 The results of long-term stability tests on the materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0028] Figure 8 A schematic diagram of the appearance of the NF / ZIF-67@NiCe (non-magnetic) material prepared for Comparative Example 1;

[0029] Figure 9 The image shows the microstructure of the NF / ZIF-67@NiCe (non-magnetic) material prepared for Comparative Example 1. Detailed Implementation

[0030] The principles and features of this application are described below with reference to embodiments. The examples are for illustrative purposes only and are not intended to limit the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0031] Currently, noble metal-based materials are known as high-performance catalysts for the oxygen evolution reaction (OER), but their scarcity and high cost severely limit their application in large-scale industrial production. Transition metal-based materials, due to their vacant d-electron orbitals and tunable electronic structures, exhibit good catalytic activity and stability in the OER and are considered ideal candidates to replace noble metal-based materials. Furthermore, compared to single-element transition metal materials, multi-component transition metal materials can effectively optimize the electronic structure and surface chemistry through the synergistic effect between different components, often resulting in superior catalytic performance.

[0032] Ion replacement technology, as an effective means of achieving material diversification, can optimize the physicochemical properties of materials and enhance their electrocatalytic oxygen evolution activity and stability by introducing heterogeneous elements into the material system, thereby controlling the electronic structure, band structure, and local coordination environment. Generally, ion replacement technology has advantages such as mild operating conditions, strong reaction controllability, and the ability to introduce target ions into the framework of materials such as molecular sieves and layered compounds. However, when the radius difference between the replacing ion and the original ion in the host material is small, the ion can autonomously drive the replacement reaction; while when the replacing ion (such as Mn)... 2+ Ce 2+and La 3+ (etc.) and the original ions in the host material (such as Co in ZIF-67) 2+ When there are significant differences in ion size, the replacement process requires overcoming high lattice energy, typically necessitating high temperature, high pressure, or other strong driving energy conditions to achieve lattice ion replacement. This not only increases the preparation cost of oxygen evolution reaction (OER) active materials but also hinders their large-scale production. However, high differences in ion size can lead to high lattice strain, lattice distortion, and coordination effects, thereby effectively regulating the electron transfer rate during electrocatalysis, optimizing the adsorption strength of intermediates, and ultimately improving the performance of the OER reaction. Based on this, this application develops a mild and low-cost ion replacement-induced strategy and applies it to the preparation of OER active materials. Specifically, this application prepares nickel-based composite material templates with metal-organic frameworks (MOFs, e.g., ZIF-67) through self-assembly. Utilizing the porous structure of the MOF as an ion replacement template and combining it with the controllable effects of magnetic fields on ion migration and material electronic properties, the controllable introduction of multi-metal active sites is ultimately achieved.

[0033] In a first aspect, this application provides a method for preparing electrode materials by magnetic field-induced ion replacement, comprising the following steps:

[0034] S1. Nickel-based materials are pre-impregnated with an aqueous solution of ligands to obtain pre-treated nickel-based materials. Imidazole ligands, through a self-assembly process (i.e., coordination), form a monolayer molecular film with a regular structure on the nickel-based surface. This film can subsequently serve as growth sites for MOF composites and influences the microstructure of the MOF composites. This step is a prerequisite for the uniform growth of metal-organic framework composites. The nickel-based material, as an electrode substrate, exhibits excellent conductivity, ensuring efficient electron transport. Furthermore, it possesses soft magnetism and can be magnetized in a magnetic field, enhancing the local magnetic field effect and promoting ion migration.

[0035] As some optional embodiments of this application, the concentration of the ligand aqueous solution is 0.5M to 3.0M, preferably 0.6M to 1.2M. The ligand aqueous solution includes at least one selected from terephthalic acid solution, 2-nitroimidazole solution, 2-methylimidazole solution, benzimidazole solution, and 2-chloroimidazole solution.

[0036] As some optional embodiments of this application, during the pre-impregnation process, the nickel-based material is impregnated in the cobalt salt solution at room temperature for 10 min to 30 min; the nickel-based material is impregnated in the ligand aqueous solution at 40°C to 70°C for 20 min to 40 min.

[0037] As some optional embodiments of the present application, the nickel-based material can be sequentially subjected to ultrasonic cleaning with ethanol, dilute hydrochloric acid and deionized water before use to remove surface impurities. The nickel-based material can be a nickel mesh, a corrugated mesh, a foamed nickel, etc. Through three-stage cleaning with organic solvents, acids and water, oil stains (ethanol dissolves organic matter), oxide layers (dilute hydrochloric acid dissolves NiO and other oxides) and residual salts (deionized water washing) on the surface of the nickel-based material are removed step by step. Ultrasonic vibration (high-frequency mechanical vibration) can enhance liquid turbulence and accelerate the separation of impurities from the substrate surface, and the cleaning can be completed in 10 minutes.

[0038] S2, the pretreated nickel-based material is subjected to repeated immersion treatment with a cobalt salt solution and an aqueous ligand solution to obtain a composite material. First, the nickel-based material is immersed in the cobalt salt solution to allow Co 2+ to be adsorbed on the surface by electrostatic adsorption; then the nickel-based material is immersed in the ligand solution (40-70°C to promote diffusion of the ligand), Co 2+ is coordinated with the ligand to form an initial MOF layer. Through repeated immersion, the MOF layer is gradually thickened by layer-by-layer self-assembly. The repeated immersion process can not only avoid local accumulation or shedding caused by one-time large growth, but also allow the load to be adjusted by the number of cycles to meet the demand for material thickness in different applications. The initial layer is directly grown on the substrate surface, and the subsequent layers are connected to the initial layer through coordination bonds, which can avoid separation from the substrate and improve the bonding force.

[0039] As some optional embodiments of the present application, the concentration of the cobalt salt solution is 0.1-1.0 M (M in the present application is the molar concentration in the concentration unit, i.e. mol / L), preferably 0.3-0.6 M. The cobalt salt solution includes at least one of CoCl2 solution, CoSO4 solution, Co(NO3)2 solution, Co(CH3COO)2•4H2O solution and CoC2O4 solution. The cobalt salt and the ligand used in the present application are both cheap and readily available chemical raw materials, and are widely available. The anions (Cl - , SO4 2- , etc.) of different cobalt salts can affect the dissolution rate and coordination activity of Co 2+ , and the steric hindrance of different ligands (such as one more methyl group in 2-methyl imidazole than in imidazole) can control the pore size and morphology of the organic metal framework, so the scheme of the present application also has structural adjustability.

[0040] As some optional embodiments of the present application, during the immersion treatment, the immersion temperature of the pretreated nickel-based material in the cobalt salt solution is room temperature, and the immersion time is 5-10 minutes; the immersion temperature of the pretreated nickel-based material in the aqueous ligand solution is 40-70°C, and the immersion time is 20-40 minutes; wherein the load of the composite material is not less than 5 mg / cm 2The load amount here refers to the load data of the metal organic framework material on the nickel base, for example, the load amount of ZIF-67 on the nickel base.

[0041] The composite material described in the present application is a composite structure formed by the metal organic framework material obtained by self-assembly of divalent cobalt ions and organic ligands and the substrate (nickel base material).

[0042] S3, configure a mixed solution of A salt solution and B salt solution as an ion replacement solution, and under the action of an applied magnetic field, use the ion replacement solution to perform an ion replacement reaction on the composite material to obtain an electrode material. The applied magnetic field can activate the soft magnetism of the nickel base material (nickel is a typical soft magnetic material and is easy to be magnetized), and through the Lorentz force, the migration of metal ions to the pores of the MOF material can be accelerated; at the same time, the spatial steric hindrance and replacement energy barrier caused by the difference in ion radius are reduced, so that ions with a larger radius difference (such as B salt) can also efficiently replace Co 2+ in the organic metal framework. The ionic radius of A salt is close to that of Co 2+ , which is easy to enter the lattice of the MOF material and maintain the stability of the skeleton structure; and A salt itself is an oxygen evolution reaction (OER) active metal (such as Fe and Ni, which are known as efficient OER catalysts), which can directly enhance the catalytic activity after being introduced. The ionic radius of B salt is quite different from that of Co 2+ , and the lattice strain can be introduced after replacement. And rare earth metals (Ce, La) or transition metals (Mn) can be used as cocatalysts to improve the OER stability.

[0043] Firstly, the present application forms a coordination bond between divalent cobalt ions (Co 2+ ) and organic ligands in a polar solvent, thereby causing self-assembly of the material to obtain a highly ordered metal organic framework material, and the uniformity of the material can be effectively improved by adding a pre-impregnation step, thereby improving the problem of unevenness of the material on the nickel base material. Secondly, in the subsequent dual ion replacement process, when there are atoms with a radius difference from the main atom in the replacement ions, the application of a magnetic field to induce and regulate the ion replacement process can enable large-radius ions to obtain stronger Lorentz force (F=qvxB) driving force due to carrying higher charge (q) and to migrate directionally, so that they can effectively overcome the steric hindrance effect. At the same time, the magnetic field disturbs the solvation layer structure of the ions, weakens their hydration shell, thereby reducing the effective ion size while optimizing the interface charge transfer process and reducing the electrostatic repulsion. These effects together enable large-radius ions to obtain additional kinetic energy and migration selectivity, thereby breaking through the radius limitation in traditional ion replacement; at the same time, the interaction of the magnetic dipoles of the magnetic field can effectively inhibit the agglomeration of the material and promote its uniform dispersion, thereby enhancing the electrical conductivity and catalytic activity of the material.

[0044] As some optional embodiments of this application, the concentration of the A salt solution or the B salt solution is 0.01M~1M, preferably 0.3M~0.6M. The substitution of A salt (with an ionic radius similar to Co) and B salt (with a large difference in radius) achieves "lattice matching" and "strain induction," respectively. A salt ensures structural stability, while B salt adjusts the electronic states and charge distribution of the material through lattice distortion, increasing the number of catalytically active sites.

[0045] As some optional embodiments of this application, salt solution A includes at least one of molybdenum salt solution, nickel salt solution and iron salt solution, and salt solution B includes at least one of manganese salt solution, cerium salt solution and lanthanum salt solution.

[0046] As some optional embodiments of this application, the molybdenum salt solution includes Na2MoO4 solution, (NH4)6Mo7O 24 The solution includes at least one of the following: Mo(C5H7O2)3 solution and (C5H5)2MoCl2 solution; the nickel salt solution includes at least one of the following: NiCl2 solution, NiSO4 solution, Ni(NO3)2 solution, Ni(CH3COO)2 solution and NiC2O4 solution; and the iron salt solution includes at least one of the following: FeCl2 solution, FeSO4 solution, Fe(NO3)3 solution, FeC6H5O7 solution and Fe2(C2O4)3 solution.

[0047] As some optional embodiments of this application, the manganese salt solution includes at least one of MnCl2 solution, Mn(NO3)2 solution, MnSO4 solution and Mn3(C6H5O7)2 solution, the cerium salt includes at least one of Ce2(SO4)3 solution, CeCl3 solution, Ce(NO3)3 solution, Ce(C6H5O7) solution and Ce(C5H7O2)3 solution, and the lanthanum salt includes at least one of La2(SO4)3 solution, LaCl3 solution, La(NO3)3 solution, La(C5H7O2)3 solution and La(C6H5O7) solution.

[0048] As some optional embodiments of this application, the strength of the external magnetic field is 0.1T~0.8T, the reaction temperature of the ion replacement reaction is 20℃~60℃, and the reaction time is 3h~6h.

[0049] Secondly, based on a general inventive concept, this application also provides an electrode material obtained by the method of magnetic field-induced ion replacement preparation of electrode materials in the first aspect.

[0050] In summary, the method for preparing electrode materials by magnetic field-induced ion replacement provided in this application has the following advantages:

[0051] (1) By introducing the magnetic field induction effect, the thermodynamic and kinetic barriers caused by the difference in ion radius can be effectively broken through, and the size mismatch limitation on the substitution process can be overcome; at the same time, the magnetic field can regulate the growth orientation of the material, increase the number of active sites of the catalytic reaction, and accelerate the process of the oxygen evolution reaction, thereby significantly improving the catalytic performance.

[0052] (2) The process steps are clear and explicit, the operating conditions are mild (normal pressure, low temperature environment), the equipment requirements are simple, high temperature calcination or high pressure equipment is not required, the energy consumption is low and the operation is safe. It is easy to realize automatic or semi-automatic control, and has excellent controllability and repeatability, providing a feasible path for large-scale industrial continuous production.

[0053] The above technical solutions of the present application will be described in detail below in conjunction with specific examples.

[0054] Example 1

[0055] The present embodiment provides a method for preparing an electrode material by magnetic field-induced ion substitution, comprising the following steps:

[0056] Step 1.1: Cut the foam nickel into a sheet shape of 2 cm x 5 cm, and sequentially clean the foam nickel (NF) with ethanol, dilute hydrochloric acid (concentration of 2M, same below) and deionized water for 10 min of ultrasonic cleaning (frequency of 40 kHz, same below) to remove surface impurities.

[0057] Step 1.2: Place the cleaned NF in a 1.2M concentration of 2-methylimidazole solution at 60°C for 30 min, take it out, and wash it with deionized water to obtain a pretreated nickel base.

[0058] Step 1.3: Dip the pretreated nickel at room temperature in a 0.6M concentration of cobalt nitrate solution for 5 min, then dip it in a 1.2M concentration of 2-methylimidazole solution at 60°C for 30 min; repeat the above dipping step twice to make the pretreated nickel base material (NF material) grow uniformly on the surface of the purple ZIF-67 material, i.e. to obtain the NF / ZIF-67 material; the loading amount of the NF / ZIF-67 material is 7.2 mg / cm 2 .

[0059] Step 1.4: Prepare 200 mL of 0.075M concentration of nickel nitrate solution and 0.025M concentration of cerium nitrate solution in a 250 mL beaker, and then place the beaker in the center of the magnetic device with a magnetic field strength of 0.2T, as shown in Figure 1 .

[0060] Step 1.5: Then vertically hang the NF / ZIF-67 material prepared in step 1.3 in the beaker, react at 30°C for 5h, and take it out after complete reaction, as shown inFigure 2 As shown, the purple color on the substrate completely disappeared. After washing with deionized water and drying, the final magnetic field-induced prepared NF / ZIF-67@NiCe (with magnet) composite electrode material was obtained, and the Ce content was 11.96wt%.

[0061] Figure 3 The micro-morphology diagram of the NF / ZIF-67@NiCe (with magnet) composite electrode material is shown in FIG. 4. Figure 3 As shown, the SEM test of the NF / ZIF-67@NiCe (with magnet) material observed that it was uniform flake-shaped, had a large specific surface area and active sites.

[0062] Figure 4 The XRD test result of the NF / ZIF-67@NiCe (with magnet) composite electrode material confirmed that the NiCe element could be successfully doped and replaced by the magnetic field effect;

[0063] Figure 5 The XPS test result of the NF / ZIF-67@NiCe (with magnet) composite electrode material confirmed that the Co binding energy in the NF / ZIF-67@NiCe (with magnet) material appeared to shift, indicating the successful doping of the element.

[0064] Example 2

[0065] The present embodiment provides a method for preparing an electrode material by magnetic field-induced ion replacement, comprising the following steps:

[0066] Step 2.1: Cut the nickel foam into a sheet shape of 2cm x 5cm, and sequentially clean the nickel foam (NF) with ethanol, dilute hydrochloric acid and deionized water by ultrasonic cleaning to remove surface impurities.

[0067] Step 2.2: Place the cleaned NF at 70°C in a 2-methylimidazole solution with a concentration of 0.5M for 40min, take it out, and clean it with deionized water to obtain a pretreated nickel base.

[0068] Step 2.3: Dip the pretreated nickel at room temperature in a 0.1M cobalt nitrate solution for 10min, take it out and then dip it in a 2-methylimidazole solution with a concentration of 0.5M at 70°C for 40min, and repeat the above dipping step twice, so that the pretreated nickel base material (NF material) grows uniformly on the surface of the purple ZIF-67 material, i.e. NF / ZIF-67 material is obtained; the loading of the NF / ZIF-67 material is 10.6mg / cm 2 .

[0069] Step 2.4: A 200 mL solution of nickel nitrate with a concentration of 0.5 M and a solution of lanthanum nitrate with a concentration of 0.5 M were prepared in a 250 mL beaker, and the beaker was placed in the center of the magnetic device with a magnetic field strength of 0.6 T.

[0070] Step 2.5: The NF / ZIF-67 material prepared in step 2.3 was vertically hung in the beaker, and the reaction was carried out at 60°C for 3 h. After complete reaction, the purple color on the substrate completely disappeared. After washing with deionized water and drying, the NF / ZIF-67@NiLa (magnetic) composite electrode material was obtained, and the La content was 13.2 wt%.

[0071] Example 3

[0072] The present embodiment provides a method for preparing an electrode material by magnetic field-induced ion replacement, comprising the following steps:

[0073] Step 3.1: The foam nickel was cut into a sheet shape of 2 cm x 5 cm, and the foam nickel (NF) was sequentially ultrasonically cleaned with ethanol, dilute hydrochloric acid, and deionized water to remove surface impurities.

[0074] Step 3.2: The cleaned NF was placed in a 2-methylimidazole solution with a concentration of 3 M at 40°C for 20 min, taken out, and washed with deionized water to obtain a pretreated nickel base.

[0075] Step 3.3: The pretreated nickel was immersed in a 1.0 M cobalt nitrate solution at room temperature for 5 min, and then immersed in a 3 M 2-methylimidazole solution at 40°C for 20 min. The above immersion step was repeated twice to make the pretreated nickel base material (NF material) grow uniformly on the surface of the purple ZIF-67 material, i.e., to obtain the NF / ZIF-67 material. The loading amount of the NF / ZIF-67 material was 8.2 mg / cm 2 .

[0076] Step 3.4: A 200 mL solution of nickel nitrate with a concentration of 0.5 M, a solution of iron nitrate with a concentration of 0.25 M, and a solution of manganese nitrate with a concentration of 0.5 M were prepared in a 250 mL beaker, and the beaker was placed in the center of the magnetic device with a magnetic field strength of 0.8 T.

[0077] Step 3.5: The NF / ZIF-67 material prepared in step 3.3 was vertically hung in the beaker, and the reaction was carried out at 50°C for 6 h. After complete color change, it was taken out. After washing with deionized water and drying, the NF / ZIF-67@NiFeMn (magnetic) composite electrode material was obtained, and the Mn content was 10.2 wt%.

[0078] Example 4

[0079] The embodiment provides a method for preparing an electrode material through magnetic field-induced ion replacement, and comprises the following steps:

[0080] Step 4.1: The nickel foam is cut into a sheet shape with a size of 2 cm*5 cm, and the nickel foam (NF) is sequentially subjected to ultrasonic cleaning with ethanol, dilute hydrochloric acid and deionized water to remove surface impurities.

[0081] Step 4.2: The cleaned nickel foam is placed in a 2-methylimidazole solution with a concentration of 1.5 M at 60 ℃ for 30 min, taken out, and cleaned with deionized water to obtain a pretreated nickel base.

[0082] Step 4.3: The pretreated nickel is immersed in a cobalt nitrate solution with a concentration of 0.6 M at room temperature for 5 min, and then immersed in a 2-methylimidazole solution with a concentration of 1.5 M at 60 ℃ for 30 min; the aforementioned immersion step is repeated twice, so that the pretreated nickel base material (NF material) is uniformly grown with purple ZIF-67 material on the surface, that is, the NF / ZIF-67 material is obtained; the loading amount of the NF / ZIF-67 material is 5.6 mg / cm 2 .

[0083] Step 4.4: 200 mL of a nickel nitrate solution with a concentration of 0.075 M, 0.025 M of an iron nitrate solution, 0.05 M of a cerium nitrate solution and 0.05 M of a lanthanum nitrate solution are prepared and placed in a 250 mL beaker, and then the beaker is placed at the center of a magnetic device with a magnetic field strength of 0.2 T.

[0084] Step 4.5: The NF / ZIF-67 material prepared in step 4.3 is vertically hung in the beaker, and the reaction is carried out at 20 ℃ for 3 h, and then the NF / ZIF-67 material is taken out after complete discoloration. After being cleaned with deionized water and dried, the NF / ZIF-67@NiFeCeLa (magnetic field induction) composite electrode material prepared through magnetic field induction is obtained, and the content of Ce is 9.36 wt%, and the content of La is 8.64 wt%.

[0085] Comparative Example 1

[0086] The comparative example provides a method for preparing an electrode material through ion replacement without magnetic field induction, comprising the following steps:

[0087] (1) The nickel foam is cut into a sheet shape with a size of 2 cm*5 cm, and the nickel foam (NF) is sequentially subjected to ultrasonic cleaning with ethanol, dilute hydrochloric acid and deionized water to remove surface impurities.

[0088] (2) The cleaned NF is placed in a 0.6M cobalt nitrate solution at room temperature (25°C) for 10 minutes of pre-impregnation, and then placed in a 1.2M 2-methylimidazole solution at 60°C for 30 minutes of reaction, taken out, and washed with deionized water to obtain a pretreated nickel base.

[0089] (3) The pretreated nickel base is placed in a 0.6M cobalt nitrate solution at room temperature for 5 minutes of impregnation, taken out, and then placed in a 1.2M 2-methylimidazole solution at 60°C for 30 minutes of impregnation; the aforementioned impregnation step is repeated twice to make the pretreated nickel base material (NF material) surface uniformly grow purple ZIF-67 material, i.e., to obtain NF / ZIF-67 material; the loading of the NF / ZIF-67 material is 7.8mg / cm 2 It is explained here that the same process cannot guarantee that the loading is completely consistent, but it is within the scope of the present application.

[0090] (4) A 200mL 0.075M nickel nitrate solution and a 0.025M cerium nitrate solution are prepared and placed in a 250mL beaker, and then uniformly dissolved and dispersed. The NF / ZIF-67 material is vertically hung in the beaker for ion replacement, and the reaction is carried out at 30°C for 5h, as shown in Figure 8 It can be seen that the color of the material does not completely change, indicating that the material cannot be completely replaced. After washing with deionized water and drying, the NF / ZIF-67@NiCe (without magnetic field) composite electrode material prepared under the condition of no magnetic field is obtained, and the SEM micro-morphology is shown in Figure 9 It can be observed that the specific surface area is small, and the material is in the form of thick blocks, and the Ce content is 1.89wt%.

[0091] Comparative Example 2

[0092] The present comparative example provides a method for preparing an electrode material by single-element magnetic field assisted ion replacement, comprising the following steps:

[0093] (1) The nickel foam is cut into a sheet shape of 2cm x 5cm, and the nickel foam (NF) is ultrasonically cleaned with ethanol, dilute hydrochloric acid, and deionized water in sequence to remove surface impurities.

[0094] (2) The cleaned NF is placed in a 0.6M cobalt nitrate solution at room temperature (25°C) for 10 minutes of pre-impregnation, and then placed in a 1.2M 2-methylimidazole solution at 60°C for 30 minutes of reaction, taken out, and washed with deionized water to obtain a pretreated nickel base.

[0095] (3) The pretreated nickel is immersed in a 0.6 M cobalt nitrate solution at room temperature for 5 min, and then taken out and immersed in a 2-methylimidazole solution with a concentration of 1.2 M at 60 °C for 30 min; the above-mentioned immersion steps are repeated twice, so that the purple ZIF-67 material is uniformly grown on the surface of the pretreated nickel-based material (NF material), that is, the NF / ZIF-67 material is obtained; the loading amount of the NF / ZIF-67 material is 7.1 mg / cm 2 .

[0096] (4) A 200 mL cerium nitrate solution with a concentration of 0.01 M is prepared and placed in a 250 mL beaker, and then the beaker is placed in the center of the magnetic equipment with a magnetic field strength of 0.2 T. The NF / ZIF-67 material is vertically hung in the beaker, and after 5 h of reaction at 30 °C, it is taken out, washed with deionized water and dried, and finally the NF / ZIF-67@Ce (with magnetic field) composite electrode material prepared by magnetic field induction is obtained, and the Ce content is 3.22 wt%.

[0097] Experimental example

[0098] The electrode materials prepared in Example 1 and Comparative Examples 1 and 2 are subjected to electrochemical activity test and long-term stability test, as follows:

[0099] (1) Figure 6 The performance comparison chart for electrochemical activity test is shown in the figure. The samples prepared in Example 1, Comparative Example 1 and Comparative Example 2 are tested in a three-electrode system (counter electrode: platinum mesh, reference electrode: Hg / HgO electrode, working electrode: sample), and the electrolyte is a 1 M alkaline electrolyte (KOH solution). Under the working condition, the reference electrode is in contact with the electrolyte through a salt bridge. Through Figure 6 the test results, it can be observed that the OER potential of the NF / ZIF-67@NiCe (with magnetic field) material prepared in Example 1 is 0.89 V at 0.5 A / cm 2 , which exhibits excellent electrochemical performance, while the electrochemical performance of the NF / ZIF-67@NiCe (without magnetic field) prepared in Comparative Example 1 and the NF / ZIF-67@Ce (with magnetic field) prepared in Comparative Example 2 is less improved than that of the commercial nickel foam. In addition, Examples 2, 3 and 4 use the same test method, and their OER potentials are 0.90 V, 0.88 V and 0.86 V, respectively.

[0100] (2) Figure 7 The long-term stability test results of the materials prepared in Example 1 and Comparative Examples 1 and 2 are shown in the figure. The cell voltage specific test process includes: using 6 M KOH as the electrolyte, Ni mesh as the cathode, the test material as the anode, and a direct current power supply of 3000 A / m 2The current density of 3000 A / m2 was used to carry out long-term stability test, and the cell voltage was monitored and recorded at certain time intervals. Figure 7 It can be seen that, at 3000 A / m2 2 Below, the NF / ZIF-67@NiCe (with magnetism) material prepared by the embodiment 1 of the present application has better activity and stability.

[0101] Although the specific embodiments of the present application are described in detail, it should not be understood as limiting the scope of protection of the present application. Various modifications and variations made by those skilled in the art within the scope described in the claims are still within the scope of protection of the present application.

Claims

1. A method for the preparation of an electrode material by magnetic field induced ion exchange, characterized in that The method comprises the following steps: pre-dipping a nickel-based material with a ligand aqueous solution to obtain a pretreated nickel-based material; repeatedly dipping the pretreated nickel-based material with a cobalt salt solution and a ligand aqueous solution to obtain a composite material; configuring a mixed solution of an A salt solution and a B salt solution as an ion replacement solution, and performing ion replacement reaction on the composite material with the ion replacement solution under the action of an applied magnetic field to obtain an electrode material; the A salt solution comprises at least one of a molybdenum salt solution, a nickel salt solution and an iron salt solution, and the B salt solution comprises at least one of a manganese salt solution, a cerium salt solution and a lanthanum salt solution; In the process of the impregnation treatment, the impregnation temperature of the pretreated nickel base in the cobalt salt solution is room temperature, and the impregnation time is 5 min to 10 min; the impregnation temperature of the pretreated nickel base in the ligand aqueous solution is 40 DEG C to 70 DEG C, and the impregnation time is 20 min to 40 min; wherein the loading of the composite material is not less than 5 mg / cm 2 ; the concentration of the ligand aqueous solution is 0.5M-3.0M, and the ligand aqueous solution comprises at least one of terephthalic acid solution, 2-nitroimidazole solution, 2-methylimidazole solution, benzimidazole solution and 2-chloroimidazole solution; during the pre-dipping process, the dipping temperature is 40℃-70℃, and the dipping time is 20min-40min; the strength of the applied magnetic field is 0.1T-0.8T, the reaction temperature of the ion replacement reaction is 20℃-60℃, and the reaction time is 3h-6h.

2. The method of claim 1, wherein the magnetic field is applied by a magnetic field source. the concentration of the cobalt salt solution is 0.1M-1.0M, and the cobalt salt solution comprises at least one of CoCl2 solution, CoSO4 solution, Co(NO3)2 solution, Co(CH3COO)2•4H2O solution and CoC2O4 solution.

3. The method of claim 1, wherein the magnetic field is applied by a magnetic field source. the concentration of the A salt solution or the B salt solution is 0.01M-1M.

4. The method of claim 1, wherein the magnetic field is applied by a magnetic field source. The molybdenum salt solution includes at least one of a Na2MoO4 solution, a (NH4)6Mo7O 24 solution, a Mo(C5H7O2)3 solution, and a (C5H5)2MoCl2 solution, the nickel salt solution includes at least one of a NiCl2 solution, a NiSO4 solution, a Ni(NO3)2 solution, a Ni(CH3COO)2 solution, and a NiC2O4 solution, and the iron salt solution includes at least one of a FeCl2 solution, a FeSO4 solution, a Fe(NO3)3 solution, a FeC6H5O7 solution, and a Fe2(C2O4)3 solution.

5. The method of claim 1, wherein the magnetic field is applied by a magnetic field source. the manganese salt solution comprises at least one of MnCl2 solution, Mn(NO3)2 solution, MnSO4 solution and Mn3(C6H5O7)2 solution, the cerium salt comprises at least one of Ce2(SO4)3 solution, CeCl3 solution, Ce(NO3)3 solution, Ce(C6H5O7) solution and Ce(C5H7O2)3 solution, and the lanthanum salt comprises at least one of La2(SO4)3 solution, LaCl3 solution, La(NO3)3 solution, La(C5H7O2)3 solution and La(C6H5O7) solution.

6. An electrode material, characterized by The electrode material is obtained by the method of any one of claims 1-5.

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