Hollow nano cage-shaped H-NiCoFe-LDH based on ZIF-67 derivation as well as preparation method and application of hollow nano cage-shaped H-NiCoFe-LDH
By preparing ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH at room temperature, the problems of low utilization of active materials in three-dimensional hierarchical structures and structural integrity under high-temperature hydrothermal conditions were solved, and efficient electrochemical performance was improved.
Patent Information
- Application Number
- CN202511671372.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-02-10
AI Technical Summary
In existing technologies, the localized dense arrangement of nanosheets in a three-dimensional hierarchical structure leads to a reduction in the volume utilization rate of the active material, and the structural integrity and performance of MOF materials synthesized under high temperature and high pressure hydrothermal conditions are affected.
ZIF-67 polyhedra were synthesized at room temperature as templates, and a core-shell structure ZIF-67/NiCo-LDH was formed by exchanging Ni2+ and Co2+ ions. Subsequently, Fe2+ ions were introduced to replace some Co2+ and Ni2+, forming a hollow nanocage-like H-NiCoFe-LDH, which maintained the polyhedral morphology and increased the number of active sites.
Hollow nanocage-like H-NiCoFe-LDH was prepared at room temperature, which improved the specific surface area and electrochemical performance of the material, avoided structural collapse and performance degradation under high temperature and high pressure conditions, and improved the utilization rate and capacitance performance of the active material.
Smart Images
Figure CN121494097A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of supercapacitors, in particular to a ZIF-67-derived hollow nanocage H-NiCoFe-LDH and a preparation method and application thereof. BACKGROUND
[0002] Among the electrode materials of supercapacitors, LDH materials have a unique layered structure, thereby having the advantage of high theoretical specific capacitance. In addition, due to the difference in preparation methods, the chemical composition and micro-morphology can be adjusted, wherein the preparation methods mainly include the coprecipitation method, the electrodeposition method and the template method.
[0003] The basic principle of the template method is to use a material with a 3D structure as a template, and then remove the template to obtain a nanostructure with a template agent, that is, an LDH material with precise morphology and size characteristics can be formed. For example, the prior art 1 (Zhou H, Sha X, Zeng F, et al. A ZIF-67 derived NiCo-LDH nanosheet-nanourchin 3D hierarchical nanostructure for high-performance supercapacitors [J]. Journal of Materials Chemistry A, 2024, 12 (31): 20191-20201.) uses urchin-like microspheres CoCu as a skeleton, then grows a regular dodecahedron ZIF-67 on the surface in situ, and finally, through a hydrothermal method, uses Ni ions to etch the polyhedral ZIF-67 into nanosheet-like NiCo-LDH, obtaining a 3D hierarchical nanostructure with a specific capacitance of 18.71 F cm -2 under the condition of 3 mA cm -2 ; after 5000 charge-discharge tests, the capacity retention rate is 83.6%. The technical effect of this technical scheme is to construct a "urchin microsphere-nanosheet" three-dimensional hierarchical nanostructure to improve the cycle stability and electrochemical performance, wherein the CoCu urchin microsphere structure provides support, and the ZIF-67-derived LDH nanosheet structure provides a high specific surface area. However, this technical scheme uses nanometer urchins as support, which effectively avoids the stacking of two-dimensional nanosheets in the plane and the structural collapse during the cycle process, however, the local dense arrangement phenomenon of nanosheets in three-dimensional space occurs, which leads to the problem that the active sites in the center region of the urchin structure cannot be fully utilized, ultimately resulting in a decrease in the volume utilization rate of the active material.
[0004] To solve the problem of reducing the volume utilization of active materials caused by the local dense arrangement of nanosheets in the three-dimensional hierarchical structure, a method of constructing a hierarchical structure directly on ZIF-67 can be used to improve the volume utilization of the material. For example, in the previous work of the inventors' research group, prior art 2 (Xu F, Xu R, Sun L, Yu C, Feng Y, Chen Y, Luo S, Li Q. Hollow nanoflower NiCo-LDH and its preparation method and application) by the synergistic regulation of solvent DMSO and surfactant CTAB, regular ZIF-67 was prepared, then ZIF-67 was used as a template and Co source, and Ni ions were used for etching by hydrothermal method to form a hollow nanoflower structure of NiCo-LDH, obtaining a specific capacitance of 1834 F g -1 under the condition of 1 A g -1 Technical effect. The basic principle of this technical solution is to directly use ZIF-67 as a template and embed DMSO molecules into the ZIF-67 framework as a morphology directing agent to induce the formation of a unique multi-level hollow "nanoflower-small ball" structure during the subsequent etching process, so that the active sites in the material can be fully utilized. However, according to the common knowledge in the art and the subsequent research of the inventors, it was found that the ion etching in this technical solution, as a necessary technical feature, needs to be carried out under high-temperature hydrothermal conditions, and the feature can cause slight changes in the micro-morphology of the obtained material under hydrothermal conditions, which can only lead to performance degradation.
[0005] The above-mentioned influence of high-temperature and high-pressure hydrothermal conditions on the structural integrity of MOF materials and further on the performance was studied in detail in prior art 3 (Wang Y, Ban Y, Hu Z, et al. Adaptive healing of stress-induced dynamic cracks in a metal-organic framework membrane using nanoparticles [J]. Science Advances, 2024, 10 (31): eado7331.) The specific content is that the MOF membrane material is placed in a high-temperature and high-pressure environment, and by observing the change in morphology, it is found that the membrane layer has stress-induced dynamic cracks. This experiment proves that under high-temperature, high-pressure and other hydrothermal conditions, stress defects will be induced in the MOF material, which will destroy the complete structure of the MOF material.
[0006] Therefore, synthesizing MOFs under mild conditions, such as low temperature and ambient pressure, can solve the above problems. For example, existing literature 4 (Li, Yumeng, et al. Enhancing the electrocatalytic activities of metalorganic frameworks for the oxygen evolution reaction with bimetallic groups. Dalton Transactions 52.47(2023):17834-17845.) synthesized CoNi-MOFs with rod-like structures by stirring and allowing them to stand at room temperature. This improved the crystallinity of the MOF material, formed a regular crystal structure, and reduced lattice defects, ultimately enhancing the rapid electron transport.
[0007] As can be seen from existing literature 4, the low-temperature synthesis method has the advantages of improving crystal structure integrity and low energy consumption compared with the conventional hydrothermal method. However, in subsequent applications of the obtained MOFs materials, such as etching, the existing technology still requires the use of the conventional hydrothermal method, that is, the reaction is carried out under high temperature conditions, which inevitably leads to a decrease in crystal structure integrity. Summary of the Invention
[0008] The purpose of this invention is to provide a ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH, its preparation method, and its applications. The basic technical principles involved in solving the problems of the prior art in this invention are as follows:
[0009] 1. Using the ZIF-67 polyhedron synthesized at room temperature as a template, and utilizing Ni 2+ Co on the surface of ZIF-67 2+ Partial ion exchange reaction occurs, and NiCo-LDH nanosheets are epitaxially grown on the surface of ZIF-67 to form a uniform core-shell structure ZIF-67 / NiCo-LDH.
[0010] 2. Introducing Fe at room temperature 2+ Further replacement of some Co through ion exchange 2+ and Ni 2+ To achieve the dissolution of the ZIF-67 core and form ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH, while maintaining the polyhedral morphology of ZIF-67, the specific surface area and number of active sites of the material are increased.
[0011] 3. Among them, Fe 2+ It serves a dual purpose:
[0012] 3.1. Regulating the microstructure of materials to form active sites;
[0013] 3.2 Accelerate the etching rate of ZIF-67 template to obtain hollow nanocage structures at room temperature.
[0014] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:
[0015] A method for obtaining ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH is described. The method uses cobalt nitrate hexahydrate, dimethylimidazole, nickel nitrate hexahydrate, and ferrous chloride tetrahydrate as raw materials. First, ZIF-67 is obtained through a static settling method. Then, a core-shell structured ZIF-67 / NiCo-LDH is obtained through a first-step ion exchange. Finally, ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH is obtained through a second-step ion exchange.
[0016] The H-NiCoFe-LDH has a polyhedral structure, exhibiting a hollow nanocage shape, with a uniform surface coating of nanosheets, the size of which is 400-600 nm.
[0017] A method for preparing ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH includes the following steps:
[0018] Step 1, Preparation of polyhedron ZIF-67: First, under certain conditions, cobalt nitrate hexahydrate is dissolved in methanol by stirring to obtain solution A. At the same time, under certain conditions, dimethylimidazole is dissolved in methanol by stirring to obtain solution B. Then, solutions A and B are mixed and reacted by stirring first and then allowing to stand. After the reaction is complete, the resulting product is washed with methanol and dried under certain conditions to obtain ZIF-67.
[0019] In step 1, the conditions for stirring and dissolving solutions A and B are both 10-20 min.
[0020] In step 1, the molar ratio of cobalt nitrate hexahydrate to dimethylimidazole is 1:8.
[0021] In step 1, the conditions for stirring first and then letting it stand are: stirring time is 60-80 min, standing time is 22-24 h, and the temperature of the entire process of stirring first and then letting it stand is room temperature.
[0022] In step 1, the drying conditions are: drying temperature at room temperature and drying time of 12-24 hours.
[0023] Step 2, preparation of core-shell structure ZIF-67 / NiCo-LDH: First, under certain conditions, ZIF-67 obtained in step 1 and nickel nitrate hexahydrate are placed in anhydrous ethanol to obtain solution C. Then, the reaction is stirred. After the reaction is completed, the product is washed with anhydrous ethanol and dried under certain conditions to obtain ZIF-67 / NiCo-LDH.
[0024] In step 2, the mass ratio of nickel nitrate hexahydrate to ZIF-67 is 3:1;
[0025] In step 2, the conditions for preparing solution C are: ultrasonic time of 20-30 min;
[0026] In step 2, the stirring reaction conditions are: the stirring reaction temperature is room temperature, and the stirring time is 90-100 min.
[0027] In step 2, the drying conditions are: the drying temperature is room temperature, and the drying time is 12-24 hours.
[0028] Step 3: Preparation of ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH. First, under certain conditions, the ZIF-67 / NiCo-LDH obtained in Step 2 is placed in methanol to obtain solution D. Then, ferrous chloride tetrahydrate is placed in solution D and stirred for etching reaction. After the reaction is complete, the obtained product is washed with methanol and dried under certain conditions to obtain H-NiCoFe-LDH.
[0029] In step 3, the mass ratio of ferrous chloride tetrahydrate to ZIF-67 / NiCo-LDH is 6:1;
[0030] In step 3, the conditions for preparing solution D are: sonication for 10-20 minutes;
[0031] In step 3, the conditions for the stirring etching reaction are: the temperature of the stirring etching reaction is room temperature, and the stirring etching reaction time is 4-5 hours.
[0032] In step 3, the drying conditions are: the drying temperature is room temperature, and the drying time is 12-24 hours.
[0033] All steps were performed at room temperature.
[0034] When ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH is used as an electrode material for supercapacitors, the charge / discharge voltage range is 0-0.45V, and the discharge current density is 1A g. -1 At that time, the specific capacitance of H-NiCoFe-LDH was 1800-1900 F g. -1 .
[0035] The beneficial technical effects of the material obtained by this invention have been demonstrated through experimental testing:
[0036] XRD analysis of H-NiCoFe-LDH material showed that H-NiCoFe-LDH possessed characteristic peaks of the LDH diffraction crystal plane.
[0037] SEM analysis of H-NiCoFe-LDH material showed that the basic microstructure of H-NiCoFe-LDH is a polyhedral structure with a surface covered with lamellar structures, and the size is 400-600 nm.
[0038] TEM analysis showed that the H-NiCoFe-LDH material exhibits a hollow nanocage structure in its microstructure.
[0039] Electrochemical testing of the H-NiCoFe-LDH material showed that the charge / discharge voltage range was 0-0.45V, and the discharge current density was 1Ag. -1 At that time, its specific capacitance was 1800-1900 F g -1 .
[0040] Therefore, the material of the present invention has the following advantages over the prior art:
[0041] 1. The entire synthesis process is carried out at room temperature, without the need for high-temperature and high-pressure hydrothermal / solventothermal conditions, reducing energy consumption and environmental pollution. At the same time, it avoids the collapse or aggregation of the microstructure of MOFs materials under high-temperature conditions, ensuring the integrity and stability of the microstructure.
[0042] 2. Successfully maintains the polyhedral structure and high porosity characteristics of ZIF-67, achieving precise control over the morphology of the product;
[0043] 3. The three metal elements Ni, Co, and Fe produce a synergistic effect, providing abundant and reversible redox reactions, increasing the Faraday pseudocapacitance, and ultimately improving the electrochemical performance of the material. Attached Figure Description
[0044] Figure 1 The XRD patterns are of ZIF-67 obtained in step 1 of Example 1, ZIF-67 / NiCo-LDH obtained in step 2, H-NiCoFe-LDH obtained in step 3, and H-NiCo-LDH obtained in Comparative Example 1.
[0045] Figure 2 The image shows the SEM image of ZIF-67 obtained in step 1 of Example 1.
[0046] Figure 3 The image shows the SEM image of ZIF-67 / NiCo-LDH obtained in step 2 of Example 1.
[0047] Figure 4 The image shows the SEM image of H-NiCoFe-LDH obtained in step 3 of Example 1.
[0048] Figure 5 The image shows a TEM image of ZIF-67 / NiCo-LDH obtained in step 2 of Example 1.
[0049] Figure 6 The charge-discharge curves of ZIF-67 / NiCo-LDH obtained in step 2 of Example 1, H-NiCoFe-LDH obtained in step 3, and H-NiCo-LDH obtained in Comparative Example 1 are shown.
[0050] Figure 7 The image shows a TEM image of H-NiCoFe-LDH obtained in step 3 of Example 1.
[0051] Figure 8 The image shows the SEM image of H-NiCo-LDH obtained in Comparative Example 1.
[0052] Figure 9 The image shows a TEM image of the H-NiCo-LDH obtained in Comparative Example 1. Detailed Implementation
[0053] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.
[0054] Example 1
[0055] A method for preparing ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH includes the following steps:
[0056] Step 1, Preparation of polyhedron ZIF-67: First, 4 mmol of cobalt nitrate hexahydrate was dissolved in 60 mL of methanol by stirring to obtain solution A. At the same time, 32 mmol of dimethylimidazole was dissolved in 80 mL of methanol by stirring to obtain solution B. Then, solutions A and B were mixed and reacted by stirring first and then allowing to stand. After the reaction was completed, the product was washed with methanol and dried at room temperature for 12 hours to obtain ZIF-67.
[0057] In step 1, the stirring and dissolving conditions for both solution A and solution B are 10 min.
[0058] In step 1, the molar ratio of cobalt nitrate hexahydrate to dimethylimidazole is 1:8.
[0059] The conditions for stirring first and then letting stand are: stirring time is 1 hour, standing time is 24 hours, and the temperature of the entire process of stirring first and then letting stand is room temperature.
[0060] To confirm the composition of ZIF-67, XRD tests were performed. The test results are as follows: Figure 1 As shown, ZIF-67 exhibits characteristic peaks. The test results confirm the successful preparation of ZIF-67.
[0061] To verify the microstructure of ZIF-67, SEM testing was performed. The test results are as follows: Figure 2 As shown, the microstructure of ZIF-67 is a polyhedral structure with a size of 400-600 nm.
[0062] Step 2, preparation of core-shell structure ZIF-67 / NiCo-LDH: First, 0.2g of ZIF-67 obtained in Step 1 and 2mmol of nickel nitrate hexahydrate were placed in 80mL of anhydrous ethanol to obtain solution C, with an ultrasonic time of 20min. Then, the reaction was stirred. After the reaction was completed, the product was washed with anhydrous ethanol and dried at room temperature for 12h to obtain ZIF-67 / NiCo-LDH.
[0063] In step 2, the conditions for the stirring reaction are: the stirring reaction temperature is room temperature and the stirring reaction time is 90 min.
[0064] To confirm the composition of ZIF-67 / NiCo-LDH, XRD tests were performed. The test results are as follows: Figure 1 As shown, ZIF-67 / NiCo-LDH exhibits characteristic peaks of both ZIF-67 and NiCo-LDH. Test results indicate that NiCo-LDH was successfully prepared / loaded in situ on ZIF-67 via step 2.
[0065] To verify the microstructure of ZIF-67 / NiCo-LDH, SEM measurements were performed. The test results are as follows: Figure 3 As shown, the basic microstructure of ZIF-67 / NiCo-LDH is not substantially different from that of ZIF-67, that is, it is a polyhedral structure with a size of 400-600nm. However, the surface of ZIF-67 / NiCo-LDH is covered by a plate-like structure. Combined with the XRD test results, it can be seen that the plate-like structure is NiCo-LDH.
[0066] To further verify the microstructure of ZIF-67 / NiCo-LDH, TEM tests were performed. The test results are as follows: Figure 5 As shown, the microstructure of ZIF-67 / NiCo-LDH exhibits a core-shell structure, where ZIF-67 is the core and NiCo-LDH is the shell.
[0067] In other words, it is not possible to etch ZIF-67 using only Ni ions under a stirring reaction time of 90 minutes.
[0068] To demonstrate the electrochemical performance of ZIF-67 / NiCo-LDH, charge-discharge tests were conducted using a three-electrode system. The test results are as follows: Figure 6 As shown, the charge / discharge voltage range is 0-0.45V, and the discharge current density is 1Ag. -1 At that time, the specific capacitance of ZIF-67 / NiCo-LDH was 953 F g. -1 .
[0069] Step 3: Preparation of ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH. First, 0.1g of the ZIF-67 / NiCo-LDH obtained in Step 2 was dissolved in 30mL of methanol to obtain solution D, with an ultrasonic time of 10min. Then, 3mmol of ferrous chloride tetrahydrate was placed in solution D and stirred for etching reaction. After the reaction was completed, the obtained product was washed with methanol and dried at room temperature for 12h to obtain hollow nanocage-like H-NiCoFe-LDH.
[0070] In step 3, the conditions for the stirring etching reaction are: the temperature of the stirring etching reaction is room temperature, and the stirring etching reaction time is 4 hours.
[0071] To confirm the composition of H-NiCoFe-LDH, XRD tests were performed. The test results are as follows: Figure 1 As shown, H-NiCoFe-LDH only exhibits the characteristic peaks of LDH, while the original characteristic peaks of ZIF-67 disappear. The test results indicate that the ZIF-67 is etched away by the stirring etching reaction in step 3.
[0072] To verify the microstructure of H-NiCoFe-LDH, SEM measurements were performed. The test results are as follows: Figure 4 As shown, the basic microstructure of H-NiCoFe-LDH is not substantially different from that of ZIF-67 / NiCo-LDH, that is, it is a polyhedral structure with a surface covered with a lamellar structure, with a size of 400-600 nm.
[0073] To further verify the microstructure of H-NiCoFe-LDH, TEM testing was performed, and the results are as follows: Figure 7As shown, H-NiCoFe-LDH exhibits a hollow nanocage structure. Comparing with step 2, it can be seen that the stirring etching reaction in step 3 etches away the ZIF-67 core structure, thus converting the solid core-shell structure ZIF-67 / NiCo-LDH into the hollow nanocage structure H-NiCoFe-LDH.
[0074] To demonstrate the electrochemical performance of H-NiCoFe-LDH, charge-discharge tests were conducted using a three-electrode system. The test results are shown in the figure. The charge-discharge voltage range was 0-0.45V, and the discharge current density was 1Ag. -1 At that time, the specific capacitance of H-NiCoFe-LDH was 1863 F g. -1 Compared with step 2, the improvement is as high as 95.5%.
[0075] To demonstrate the role of Fe ions in the technical solution in step 3, Comparative Example 1 is provided, which is an H-NiCo-LDH prepared by etching ZIF-67 with Ni ions without adding Fe ions.
[0076] Comparative Example 1
[0077] A method for preparing H-NiCo-LDH by Ni ion etching ZIF-67 is described. The steps unless otherwise specified are the same as in Example 1, except that step 3 is not required, and the stirring reaction time in step 2 is changed from 90 min to 48 h. The resulting material is named H-NiCo-LDH.
[0078] To confirm the composition of H-NiCo-LDH, XRD tests were performed. The test results are as follows: Figure 1 As shown, the XRD test results of H-NiCo-LDH are not substantially different from the characteristic peaks of ZIF-67 / NiCo-LDH obtained in step 2 and H-NiCoFe-LDH obtained in step 3 of Example 1, indicating that the characteristic peaks of LDH are present. The test results show that H-NiCo-LDH and H-NiCoFe-LDH have the same crystal structure, meaning that different etching methods have no effect on the crystal structure.
[0079] To verify the microstructure of H-NiCo-LDH, SEM measurements were performed. The test results are as follows: Figure 8 As shown, the basic microstructure of NiCo-LDH is not substantially different from that of ZIF-67 / NiCo-LDH obtained in step 2 of Example 1 and H-NiCoFe-LDH obtained in step 3, i.e., it is a polyhedral structure with a lamellar surface coating. Test results show that H-NiCo-LDH and H-NiCoFe-LDH have the same basic microstructure, meaning that different etching methods have no effect on the basic microstructure.
[0080] Furthermore, TEM measurements of H-NiCo-LDH are as described in existing literature 5 (Zhang, **ao, et al. "Regulation of morphology and electronic structure of FeCoNi layered double hydroxides for highly active and stable water oxidization catalysts." Advanced Energy Materials 11.48(2021):2102141.). Figure 9 As shown, H-NiCo-LDH also exhibits a hollow nanocage structure. Existing literature indicates that by significantly extending the etching time, H-NiCo-LDH with a hollow nanocage structure can be prepared by etching ZIF-67 using only Ni ions.
[0081] To demonstrate the electrochemical performance of H-NiCo-LDH, charge-discharge tests were conducted using a three-electrode system. The test results are as follows: Figure 6 As shown, the charge / discharge voltage range is 0-0.45V, and the discharge current density is 1Ag. -1 At that time, the specific capacitance of H-NiCo-LDH was 1340 F g. -1 Although it is higher than the ZIF-67 / NiCo-LDH obtained in step 2 of Example 1, with an improvement of 40.6%, it is still much lower than the H-NiCoFe-LDH obtained in step 3 of Example 1, with an improvement of only 71.9%.
[0082] The following conclusions can be drawn from Example 1 and Comparative Example 1:
[0083] 1. Using only Ni ions, the stirring reaction time needs to be significantly extended from 90 min to 48 h to achieve etching of ZIF-67; however, by adding Fe ions, etching of ZIF-67 can be achieved in only 4 h, which means that adding Fe ions can significantly reduce the etching time.
[0084] 2. Hollow nanocage-shaped H-NiCoFe-LDH can be prepared by etching ZIF-67 with Fe ions, which can significantly improve the electrochemical performance. The reason is that the introduction of Fe element can form an electronic synergistic effect with the original Co and Ni elements.
Claims
1. A ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH, characterized in that: Using cobalt nitrate hexahydrate, dimethylimidazole, nickel nitrate hexahydrate, and ferrous chloride tetrahydrate as raw materials, ZIF-67 was first obtained by static settling. Then, a core-shell structure ZIF-67 / NiCo-LDH was obtained through a first-step ion exchange. Finally, ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH was obtained through a second-step ion exchange.
2. The hollow nanocage-like H-NiCoFe-LDH according to claim 1, characterized in that: The basic microstructure of the H-NiCoFe-LDH is a polyhedral structure with a surface covered by a lamellar structure, exhibiting a hollow nanocage shape with a size of 400-600 nm.
3. A method for preparing ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH, characterized in that... Includes the following steps: Step 1, Preparation of polyhedron ZIF-67: First, under certain conditions, cobalt nitrate hexahydrate is dissolved in methanol by stirring to obtain solution A. At the same time, under certain conditions, dimethylimidazole is dissolved in methanol by stirring to obtain solution B. Then, solutions A and B are mixed and reacted by stirring first and then allowing to stand. After the reaction is complete, the resulting product is washed with methanol and dried under certain conditions to obtain ZIF-67. Step 2, preparation of core-shell structure ZIF-67 / NiCo-LDH: First, under certain conditions, ZIF-67 obtained in step 1 and nickel nitrate hexahydrate are placed in anhydrous ethanol to obtain solution C. Then, the reaction is stirred. After the reaction is completed, the obtained product is washed with anhydrous ethanol and dried under certain conditions to obtain ZIF-67 / NiCo-LDH. Step 3, Preparation of ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH: First, under certain conditions, the ZIF-67 / NiCo-LDH obtained in Step 2 is dissolved in methanol to obtain solution D. Then, ferrous chloride tetrahydrate is placed in solution D and stirred for etching reaction. After the reaction is complete, the obtained product is washed with methanol and dried under certain conditions to obtain ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH. All steps were performed at room temperature.
4. The preparation method according to claim 3, characterized in that: In step 1, the molar ratio of cobalt nitrate hexahydrate to dimethylimidazole is 1:
8. In step 2, the mass ratio of nickel nitrate hexahydrate to ZIF-67 is 3:1; In step 3, the mass ratio of ferrous chloride tetrahydrate to ZIF-67 / NiCo-LDH is 6:
1.
5. The preparation method according to claim 3, characterized in that: In step 1, the stirring and dissolving conditions for both solution A and solution B are 10-20 min; In step 1, the conditions for stirring first and then letting it stand are: stirring time is 60-80 min, standing time is 22-24 h, and the temperature of the entire process of stirring first and then letting it stand is room temperature. In step 1, the drying conditions are: room temperature and 12-24 hours.
6. The preparation method according to claim 3, characterized in that: In step 2, the conditions for preparing solution C are: ultrasonic time of 20-30 min; In step 2, the stirring reaction conditions are as follows: stirring time is 90-100 min, and stirring reaction temperature is room temperature; In step 2, the drying conditions are: room temperature and 12-24 hours.
7. The preparation method according to claim 3, characterized in that: In step 3, the conditions for preparing solution D are: sonication for 10-20 minutes; In step 3, the stirring etching reaction conditions are: stirring etching time is 4-5 hours, and stirring etching reaction temperature is room temperature. In step 3, the drying conditions are: room temperature and 12-24 hours.
8. The ZIF-67-derived hollow nanocage-like H-NiCoFe-LDH according to claim 1, characterized in that: When used as an electrode material for supercapacitors, the charge / discharge voltage range is 0-0.45V, and the discharge current density is 1A g. -1 At that time, the specific capacitance of H-NiCoFe-LDH was 1800-1900 F g. -1 .