ZIF-67 derived hollow material and room-temperature boronizing and vulcanizing two-step preparation method thereof
ZIF-67-derived hollow materials were prepared by stepwise borylation-sulfidation treatment at room temperature, which solved the problems of particle agglomeration and morphology damage caused by high-temperature treatment, and achieved a supercapacitor electrode material with high specific capacitance and good rate performance.
Patent Information
- Application Number
- CN202511630529.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-10
- Publication Date
- 2026-02-10
AI Technical Summary
In the preparation of supercapacitor electrode materials, the high-temperature treatment in the existing technology causes the material particles to agglomerate and the morphology to be damaged, which affects the specific surface area and the accessibility of active sites, making it difficult to meet the requirements of high power and long life.
A room-temperature stepwise borylation-sulfidation treatment strategy was adopted to synthesize ZIF-67 material by room-temperature precipitation, and CoNi-LDH nanosheets were grown on its surface. Subsequently, borylation and sulfidation treatments were performed to form a complete hollow structure with nanosheet surface, avoiding material sintering and morphology damage caused by high temperature.
It significantly improves the accessibility of active sites and reaction kinetics of the material, enhances specific capacitance and rate performance. The specific capacitance of the material reaches 1550-1620 F g-1 in the 0-0.5V range, retains 70-80% at a current density of 10 A g-1, and maintains good stability during 5000 cycles.
Smart Images
Figure CN121494094A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of supercapacitors, in particular to a ZIF-67 derived hollow material and a two-step room-temperature borization and sulfuration preparation method thereof. BACKGROUND
[0002] With the rapid development of portable electronic devices, the design and manufacture of high-energy and high-power density energy storage devices have become the focus of global attention. In recent years, hybrid supercapacitors, as a new type of chemical energy storage device, have attracted much attention due to their fast charging and discharging capacity, low cost, long cycle life and high power density. Electrode materials, as a key component, are driving many researchers to develop new materials to further improve their electrochemical performance.
[0003] Metal-organic frameworks (MOFs) are considered as a promising electrode candidate material for supercapacitors due to their tunable ultrahigh specific surface area, hierarchical pore network and precisely designed morphology. MOFs and their derived systems not only have diverse redox active centers brought by rich metal nodes and organic ligands, but also can realize the optimization of ion / electron transport paths through topological structure regulation. However, the original MOFs are generally limited by the problems of low intrinsic conductivity and insufficient electrochemical stability, which are difficult to directly meet the needs of high power and long life devices. Therefore, researchers have proposed several strategies to break through the bottleneck: on the one hand, MOFs are used as precursors to obtain porous carbon, metal oxides / sulfides / phosphides with MOF skeleton characteristics through high-temperature carbonization, sulfuration or phosphatization, which significantly improves the conductivity and active site density; on the other hand, MOFs are used as sacrificial templates to reconstruct new materials with specific pore size distribution and metal dispersion state through etching or ion exchange, realizing the synergistic optimization of structure / component.
[0004] For example, the existing patent (Ni-Co-S nanopolyhedral material with hollow structure and preparation and application thereof, CN113336279B) uses ZIF-67 as a template, introduces Ni 2+ to form a nickel-cobalt double-metal-layered hydroxide (LDH) precursor, and then performs high-temperature sulfuration reaction with sulfur powder at 240-260 DEG C to obtain a Ni-Co-S nanopolyhedral material with a hollow structure for use as an electrode material. However, the sulfuration process needs to be annealed (1-2 hours) in an inert atmosphere at about 250 DEG C. However, there is a certain safety risk in using solid sulfur powder as a sulfur source under heating conditions, and the sulfuration uniformity may not be as good as liquid-phase reaction.
[0005] For example, existing literature 1 (Selective and efficient adsorption of H3BO3 from Salt Lake brine solution by ZIF-67-derived hollow cobalt sulfide[J]. Desalination, 2025.) employs a hydrothermal sulfidation strategy: ZIF-67 is mixed with thioacetamide and reacted at 120℃ for 4 hours to synthesize hollow Co3S4 polyhedral nanomaterials. Although the material prepared by this method exhibits a relatively uniform hollow polyhedral morphology, its synthesis process depends on high temperature and high pressure conditions, has a long reaction cycle, and the product shows obvious particle agglomeration, leading to a decrease in specific surface area and reduced accessibility of active sites, which to some extent limits its electrochemical performance.
[0006] Existing literature 2 (A Sulfur-Host Design for Adsorption / Catalysis Strong Synergy on Polysulfide Conversions via CoB / NCPS Composites Inheriting the Polyhedron Morphology of Metal-Organic Framework[J]. Chemical Engineering Journal, 2024.) reports a method for preparing a composite material: using ZIF-67 as a precursor and NaBH4 as a boron source, partial borylation is first performed, followed by heat treatment at 450℃ in an inert atmosphere for 3 hours, finally obtaining a nitrogen-doped carbon polyhedral shell-supported cobalt boride (CoB / NCPS) material. However, this method has the following limitations: First, high-temperature heat treatment easily causes particle agglomeration, affecting the material dispersibility and exposure of active sites; second, during the carbonization process after partial borylation, the interior of the material gradually changes from polyhedron to sphere, which to some extent destroys the original regular polyhedral morphology of ZIF-67, and may weaken the structural advantages of its precursor. Summary of the Invention
[0007] The purpose of this invention is to provide a ZIF-67-derived hollow material and its two-step preparation method using room temperature borosilicate treatment.
[0008] According to the applicant's research, a room-temperature stepwise borylation-sulfidation treatment strategy can achieve a mild and controllable structural evolution of ZIF-67 materials without the use of high temperatures. This method not only avoids material sintering and morphological damage caused by high temperatures, but also helps to form a uniform structure with open hollow and nanosheet surfaces, thereby significantly improving the accessibility of active sites and reaction kinetics, ultimately enhancing its specific capacitance and rate performance in electrochemical applications.
[0009] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:
[0010] A ZIF-67-derived hollow material and its two-step preparation method using room temperature borylation and sulfidation: First, rhombic dodecahedral ZIF-67 is synthesized via room temperature precipitation, and then Ni is introduced... 2+ CoNi-LDH nanosheets were grown on its surface to form a core-shell structure. Then, a boronizing treatment was performed at room temperature to obtain ZIF67@CoNi-LDH-B, forming a core-shell and hollow coexisting structure with nanosheets distributed on the surface. Finally, a sulfurizing treatment was performed at room temperature to obtain ZIF67@CoNi-LDH-BS, forming a complete hollow structure with nanosheets distributed on the surface. The boronizing treatment selectively etched the material, transforming it from a complete core-shell structure into a transitional structure that is partially hollow and partially retains the core-shell. The sulfurizing treatment further completed the final structural transformation and surface refinement, transforming all materials into complete hollow structures with nanosheet surfaces.
[0011] The preparation method of ZIF-67 derived hollow materials based on a two-step room temperature borylation-sulfidation process includes the following steps:
[0012] Step 1, preparation of ZIF-67: First, a certain mass of 2-methylimidazole is weighed and dissolved in methanol to obtain solution A; simultaneously, a certain mass of cobalt nitrate hexahydrate is weighed and dissolved in methanol to obtain solution B; then, solution A and solution B are mixed to obtain mixed solution C. After that, solution C is stirred and reacted under certain conditions, allowed to stand, and finally, the obtained product is washed by centrifugation with methanol and then vacuum dried under certain conditions to obtain ZIF-67 with a smooth dodecahedral structure.
[0013] Preferably, in step 1, the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is (1-1.5):1; the conditions for the room temperature precipitation method in step 1 are: reaction temperature of 20-30℃, reaction time of 10-50 min, and standing time of 12-36 h; the drying conditions are: drying temperature of 50-100℃ and drying time of 6-20 h.
[0014] Step 2, preparation of ZIF-67@CoNi-LDH: First, ZIF-67 obtained in Step 1 is dispersed in an ethanol solution at a certain mass ratio to obtain solution D; simultaneously, a certain mass of nickel nitrate hexahydrate is weighed and dissolved in an ethanol solution to obtain solution E. Then, solution D and solution E are mixed to obtain mixed solution F. After that, solution F is stirred and reacted under certain conditions. Finally, the obtained product is washed by centrifugation with methanol and then vacuum dried under certain conditions to obtain ZIF-67@CoNi-LDH with a core-shell structure on the surface having nanosheets distributed on it.
[0015] Preferably, in step 2, the mass ratio of ZIF-67 to nickel nitrate hexahydrate is 1:(2-2.5); in step 2, the conditions for room temperature synthesis are: reaction temperature of 20-30℃ and reaction time of 60-120 min; the drying conditions are: drying temperature of 50-100℃ and drying time of 6-20 h.
[0016] Step 3, Preparation of ZIF-67@CoNi-LDH-B: First, the ZIF-67@CoNi-LDH obtained in Step 2 is dispersed in deionized water at a certain mass ratio to obtain solution G; simultaneously, a certain mass of sodium borohydride is weighed and dissolved in deionized water to obtain solution H. Then, solution G and solution H are mixed to obtain mixed solution I. After that, solution I is stirred and reacted under certain conditions. Finally, the obtained product is filtered, washed alternately with anhydrous ethanol and deionized water, and then vacuum dried under certain conditions to obtain the transition state structure ZIF-67@CoNi-LDH-B with partial hollow and partial core-shell retention.
[0017] Preferably, in step 3, the mass ratio of ZIF-67@CoNi-LDH to sodium borohydride is 1:(19-21); in step 3, the mixed solution I is prepared by adding solution H dropwise to solution G; in step 3, the borylation treatment conditions are: reaction temperature of 20-30℃, reaction time of 10-50 min; the drying conditions are: drying temperature of 50-100℃, drying time of 6-20 h.
[0018] Step 4, Preparation of ZIF67@CoNi-LDH-BS: First, ZIF-67@CoNi-LDH-B obtained in Step 3 is dissolved in deionized water at a certain mass ratio to obtain solution J; simultaneously, a certain mass of sodium sulfide nonahydrate is weighed and dissolved in deionized water to obtain solution K. Then, solution J and solution K are mixed to obtain mixed solution L. Solution L is stirred and reacted under certain conditions. Finally, the obtained product is filtered, washed alternately with anhydrous ethanol and deionized water, and then vacuum dried under certain conditions to obtain ZIF-67@CoNi-LDH-BS with a complete hollow structure on a nanosheet surface.
[0019] Preferably, in step 4, the mass ratio of ZIF-67@CoNi-LDH-B to sodium sulfide nonahydrate is 1:(39-41); in step 4, the mixed solution L is prepared by adding solution K dropwise to solution J; in step 4, the sulfidation treatment conditions are: reaction temperature of 20-30℃, reaction time of 10-50 min; the drying conditions are: drying temperature of 50-100℃, drying time of 6-20 h.
[0020] This invention also provides an application of ZIF-67-derived hollow material based on a two-step room-temperature borylation-sulfidation process as an electrode material for supercapacitors, capable of charging and discharging within a 0-0.5V range, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 1550-1620 F g. -1 Compared to 1 Ag -1 , in 10 A g -1 At current densities, the specific capacitance retention rate is 70-80%.
[0021] The beneficial technical effects of the hollow ZIF-67-derived composite electrode material based on a two-step room-temperature borylation-sulfidation process obtained in this invention are as follows, as demonstrated by testing:
[0022] XRD, SEM and TEM tests show that ZIF-67@CoNi-LDH-BS contains only the characteristic peaks of CoNi-LDH, boron and sulfur species exist in amorphous form, the material has a dodecahedral hollow structure and nanosheets distributed on the surface.
[0023] XPS testing of this invention revealed that ZIF-67@CoNi-LDH-BS contains Ni, Co, B, S, O, and C elements; Co has +2, +3, and 0 valence states; Ni has +2 and +3 valence states; lattice oxygen, oxygen vacancies, and chemically adsorbed or dissociated oxygen or OH species are present; SO and metal-S bonds are present; metal-boron (MB) bonds are present; after borylation treatment, the characteristic peaks of Co 2p3 / 2 and Ni 2p3 / 2 shift negatively, indicating that the high-valence metal is reduced to the low-valence metal, corresponding to a reduction reaction; after further sulfidation treatment, Co 2p3 / 2 shifts negatively, and Co... 2+ Reduced to the more stable lower valence states of metals Co and Ni 2+ It was oxidized into Ni, which has higher stability and stronger electrochemical performance. 3+ It can be seen that the puffing-vulcanization treatment is beneficial to optimizing the electronic structure.
[0024] Electrochemical testing of this invention shows that, within the charging and discharging range of 0-0.5V, ZIF-67@CoNi-LDH-BS exhibits performance at a current density of 1 A g. -1 At that time, the specific capacitance of ZIF-67@CoNi-LDH-BS was 1550-1620 F g. -1 Compared to 1 Ag -1 , in 10A g -1 At current densities, its specific capacity retention rate is 70-80%.
[0025] Electrochemical cycling tests of this invention show that at 10 A g -1 At the specified current density, the specific capacitance retention rate is 78-85% over 5000 cycles.
[0026] Therefore, the ZIF-67 derived hollow material and its two-step room-temperature borosilicate preparation method of the present invention have the following advantages over the prior art:
[0027] 1. The room temperature, stepwise liquid phase borylation-sulfidation strategy is adopted, which does not require high temperature and high pressure equipment. It has the advantages of mild conditions, low energy consumption, and safe and simple operation. It effectively avoids the problems of particle agglomeration and structural collapse caused by high temperature treatment and is easy to prepare on a large scale.
[0028] 2. The prepared ZIF67@CoNi-LDH-BS material has a uniform and complete hollow structure and nanosheet surface, which exposes more active sites and optimizes the ion / electron transport path, thereby significantly improving the specific capacitance and rate performance of the material. Attached Figure Description
[0029] Figure 1 The image shows the XRD pattern of ZIF-67 in Example 1.
[0030] Figure 2 Here is a SEM image of ZIF-67 in Example 1;
[0031] Figure 3 The XRD patterns of ZIF-67@CoNi-LDH, ZIF-67@CoNi-LDH-B, and ZIF-67@CoNi-LDH-BS in Example 1 are shown below.
[0032] Figure 4a and Figure 4b The images shown are SEM and TEM images of ZIF-67@CoNi-LDH from Example 1.
[0033] Figure 5a and Figure 5b The images shown are SEM and TEM images of ZIF-67@CoNi-LDH-B in Example 1, respectively.
[0034] Figure 6a and Figure 6b The images shown are SEM and TEM images of ZIF-67@CoNi-LDH-BS in Example 1, respectively.
[0035] Figure 7 The image shown is a SEM-EDS image of ZIF-67@CoNi-LDH-BS in Example 1.
[0036] Figures 8a to 8f XPS images of ZIF-67@CoNi-LDH, ZIF-67@CoNi-LDH-B, and ZIF-67@CoNi-LDH-BS in Example 1;
[0037] Figure 9 The cyclic voltammetry of ZIF-67@CoNi-LDH, ZIF-67@CoNi-LDH-B, and ZIF-67@CoNi-LDH-BS at a scan rate of 5 mV / s is shown in Example 1.
[0038] Figure 10 For ZIF-67@CoNi-LDH, ZIF-67@CoNi-LDH-B, and ZIF-67@CoNi-LDH-BS in Example 1, at 1 A g -1 Charge-discharge curves at current density;
[0039] Figure 11 The specific capacitance diagrams of ZIF-67@CoNi-LDH, ZIF-67@CoNi-LDH-B, and ZIF-67@CoNi-LDH-BS under different current densities are shown in Example 1.
[0040] Figure 12This is a cycle life curve of ZIF-67@CoNi-LDH-BS in Example 1;
[0041] Figure 13a and Figure 13b The XRD and SEM images of ZIF-67@CoNi-LDH-BS-120℃ in Comparative Example 1 are shown below.
[0042] Figure 14 The cyclic voltammograms of ZIF-67@CoNi-LDH-BS-1 at 5 mV / s scan rate and at 1 A g in Comparative Example 1 are shown. -1 Charge-discharge curves at current density;
[0043] Figure 15a and Figure 15b The images are XRD and SEM images of ZIF-67@CoNi-LDH-S in Comparative Example 2, respectively.
[0044] Figure 16 The cyclic voltammograms of ZIF-67@CoNi-LDH-S in Comparative Example 2 at a scan rate of 5 mV / s and at 1 Ag -1 Charge-discharge curves at current density;
[0045] Figure 17a and Figure 17b The images are XRD and SEM images of ZIF-67@CoNi-LDH-SB in Comparative Example 3, respectively.
[0046] Figure 18 The cyclic voltammograms of ZIF-67@CoNi-LDH-SB at a scan rate of 5 mV / s and at 1 A g in Comparative Example 3 are shown. -1 Charge-discharge curves at current density. Detailed Implementation
[0047] 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.
[0048] Example 1:
[0049] A method for preparing ZIF-67-derived hollow materials based on a two-step room-temperature borylation-sulfidation process includes the following steps:
[0050] Step 1, Preparation of ZIF-67: First, 3.28 g of 2-methylimidazole was weighed and dissolved in 250 mL of methanol solution to obtain solution A. Simultaneously, 2.91 g of cobalt nitrate hexahydrate was weighed and dissolved in 250 mL of methanol solution to obtain solution B. Then, solution B was quickly poured into solution A to obtain mixed solution C. Next, solution C was stirred and reacted at a reaction temperature of 25℃ for a reaction time of 30 min. After that, it was allowed to stand for 24 h. Finally, the product obtained from the reaction was washed by centrifugation with methanol and then vacuum dried at a drying temperature of 80℃ for a drying time of 6 h to obtain ZIF-67 with a smooth dodecahedral structure.
[0051] To verify the material composition of the obtained ZIF-67 material, XRD tests were performed. The results are as follows: Figure 1 As shown, by comparing with the standard PDF card, it can be seen that ZIF-67 with no impurities, high purity and high crystallinity was successfully synthesized.
[0052] To verify the microstructure of ZIF-67, SEM testing was performed. The results are as follows: Figure 2 As shown, ZIF-67 has a uniform morphology and a smooth surface, forming a regular dodecahedral structure. As a precursor, it can serve as a framework structure.
[0053] Step 2, preparation of ZIF-67@CoNi-LDH: First, 0.2 g of ZIF-67 obtained in Step 1 was weighed and dissolved in 100 mL of ethanol solution to obtain solution D. At the same time, 0.45 g of nickel nitrate hexahydrate was weighed and dissolved in 25 mL of ethanol solution to obtain solution E. Then, solution E was quickly poured into solution D to obtain mixed solution F. Next, solution F was stirred and reacted at a reaction temperature of 25℃ and a reaction time of 90 min. Finally, the product obtained from the reaction was washed by centrifugation with methanol and then vacuum dried at a drying temperature of 60℃ and a drying time of 12 h to obtain ZIF-67@CoNi-LDH with a core-shell structure and nanosheets distributed on the surface.
[0054] To verify the material composition of the obtained ZIF-67@CoNi-LDH material, XRD tests were performed. The results are as follows: Figure 3 As shown, the diffraction peaks of ZIF-67@CoNi-LDH correspond to those of Co(OH)2 and Ni(OH)2 ⇌ 0.75H2O on the standard PDF card, and also contain the characteristic peaks of ZIF-67. The test results indicate that ZIF-67 and Ni… 2+ During the ion exchange reaction, the sample retained the framework structure of ZIF-67, while a portion was converted into CoNi-LDH.
[0055] To verify the microstructure of ZIF-67@CoNi-LDH, SEM measurements were performed. The results are as follows: Figure 4a As shown, ZIF-67@CoNi-LDH largely retains the dodecahedral structure of ZIF-67. Simultaneously, uniform CoNi-LDH nanosheets are grown on the surface of ZIF-67 through ion exchange reactions. Test results indicate that the sheet-like stacked structure is beneficial for increasing the contact area between the material and the electrolyte, facilitating the penetration of electrolyte ions.
[0056] To further verify the structural composition of ZIF-67@CoNi-LDH, TEM tests were performed. The results are as follows: Figure 4b As shown, ZIF-67@CoNi-LDH exhibits an eggshell-like core-shell structure, consistent with XRD results, confirming that ZIF-67 was partially etched and not completely converted into CoNi-LDH. Its surface consists of stacked thin lamellar layers. This structure increases the contact area between the material and the electrolyte, which is beneficial for improving the material's electrochemical performance.
[0057] To further verify the composition of ZIF-67@CoNi-LDH, XPS testing was performed. The test results are as follows: Figure 8a As shown, ZIF-67@CoNi-LDH contains characteristic peaks of Ni, Co, O, and C;
[0058] The test results for Co element are as follows: Figure 8b As shown, fitting peaks appear at 780 eV and 795.3 eV, indicating that Co has a +3 valence state; fitting peaks appear at 781.4 eV and 797.3 eV, indicating that Co has a +2 valence state;
[0059] Ni element test results are as follows Figure 8c As shown, fitting peaks appear at 854.9 eV and 874.4 eV, indicating that Ni has a +3 valence state; fitting peaks appear at 854.5 eV and 856.3 eV, indicating that Ni has a +2 valence state.
[0060] XPS test results show that the generated CoNi-LDH grew on the ZIF-67 surface after the ion exchange reaction.
[0061] To demonstrate the electrochemical performance of ZIF-67@CoNi-LDH, the ZIF-67@CoNi-LDH obtained in step 2 was subjected to electrochemical performance testing. The specific method for the electrochemical performance testing was as follows: the test material was used as the working electrode, a mercuric oxide electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and a 6M KOH solution as the electrolyte.
[0062] The cyclic voltammetry test results of ZIF-67@CoNi-LDH are as follows: Figure 9 As shown, at 5 mV s -1 Under these conditions, the area enclosed by the cyclic voltammetry test curves of ZIF-67@CoNi-LDH is the smallest. The test results indicate that ZIF-67@CoNi-LDH has a relatively small specific capacitance.
[0063] The charge-discharge test results of ZIF-67@CoNi-LDH are as follows: Figure 10 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1A g -1 At that time, the specific capacitance of ZIF-67@CoNi-LDH was 1104 F g. -1 .
[0064] The charge-discharge test results of ZIF-67@CoNi-LDH at different current densities are as follows: Figure 11 As shown, the specific capacitance of ZIF-67@CoNi-LDH decreases rapidly with increasing current density. Test results indicate that ZIF-67@CoNi-LDH has poor rate performance.
[0065] Step 3, Preparation of ZIF-67@CoNi-LDH-B: First, 50 mg of ZIF-67@CoNi-LDH obtained in Step 2 was weighed and dissolved in 50 mL of deionized water to obtain solution G. Simultaneously, 1 g of sodium borohydride was weighed and dissolved in 20 mL of deionized water to obtain solution H. Then, solution H was added dropwise to solution E to obtain solution I. After that, solution I was stirred and reacted at a reaction temperature of 25℃ for a reaction time of 30 min. Finally, the obtained product was filtered, washed alternately with anhydrous ethanol and deionized water, and then vacuum dried at a drying temperature of 60℃ for a drying time of 10 h to obtain the transition state structure ZIF-67@CoNi-LDH-B with partial hollow and partial core-shell retention.
[0066] To verify the material composition of the obtained ZIF-67@CoNi-LDH-B material, XRD tests were performed. The results are as follows: Figure 3 As shown, no boron-containing components were found in the diffraction peaks of ZIF-67@CoNi-LDH-B. Furthermore, comparing it with the diffraction peaks of ZIF-67@CoNi-LDH from step 2, the ZIF-67@CoNi-LDH-B sample still contains the characteristic peaks of ZIF-67 and CoNi-LDH, but the diffraction peak intensities are reduced. The test results indicate that the expansion treatment reduced the crystallinity of the material, suggesting that boron exists in an amorphous form.
[0067] To verify the microstructure of ZIF-67@CoNi-LDH-B, SEM measurements were performed. The results are as follows: Figure 5a As shown, the dodecahedral structure is largely preserved, and a large number of small-sized wrinkled nanosheets are formed on the surface, which helps to increase the active sites of the material.
[0068] To further verify the structural composition of ZIF-67@CoNi-LDH-B, TEM tests were performed. The results are as follows: Figure 5b As shown, ZIF-67@CoNi-LDH-B exhibits a transitional structure that is partially hollow and partially retains its core and shell.
[0069] To further verify the composition of ZIF-67@CoNi-LDH-B, XPS testing was performed. The test results are as follows: Figure 8a As shown, ZIF-67@CoNi-LDH-B contains characteristic peaks of Ni, Co, B, O, and C;
[0070] The test results for Co element are as follows: Figure 8b As shown, the Ni element test results are as follows: Figure 8c As shown, the characteristic peaks of Co 2p3 / 2 and Ni 2p3 / 2 undergo a negative shift after boronization.
[0071] XPS test results show that room temperature borylation treatment with NaBH4 reduces some high-valence metals to low-valence Ni. 2+ / Co 2+ This is conducive to the progress of redox reactions.
[0072] To demonstrate the electrochemical performance of ZIF-67@CoNi-LDH-B, electrochemical performance tests were conducted.
[0073] The cyclic voltammetry test results of ZIF-67@CoNi-LDH-B are as follows: Figure 9 As shown, at 5 mV s -1 The test results, compared with those obtained in step 2 for ZIF-67@CoNi-LDH, show that the area enclosed by the cyclic voltammetry curve of ZIF-67@CoNi-LDH-B is larger, indicating a significant increase in the specific capacitance of ZIF-67@CoNi-LDH-B. The positions of the redox peaks show significant changes, a phenomenon consistent with XPS test results, indicating that the valences of Co and Ni elements change during the borylation process.
[0074] The charge / discharge test results of ZIF-67@CoNi-LDH-B are as follows: Figure 10 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1A g -1At that time, the specific capacitance of ZIF-67@CoNi-LDH-B was 1520 F g. -1 The test results, compared with the ZIF-67@CoNi-LDH obtained in step 2, show that the boronizing treatment in step 3 can improve the specific capacitance performance by 138%.
[0075] The charge-discharge test results of ZIF-67@CoNi-LDH-B at different current densities are as follows: Figure 11 As shown, the specific capacitance of ZIF-67@CoNi-LDH-B decreases only slightly with increasing current density. Comparing the test results with those of ZIF-67@CoNi-LDH obtained in step 2, it can be seen that the boronizing treatment in step 3 improves the rate performance of the electrode material.
[0076] Step 4, Preparation of ZIF-67@CoNi-LDH-BS: First, weigh 50 mg of ZIF-67@CoNi-LDH-B obtained in Step 3 and dissolve it in 50 mL of deionized water to obtain solution J. Simultaneously, weigh 2 g of sodium sulfide nonahydrate and dissolve it in 20 mL of deionized water to obtain solution K. Then, add solution K dropwise to solution J to obtain solution L. After that, stir the reaction of solution L at a reaction temperature of 25℃ and a reaction time of 30 min. Finally, filter the obtained product, wash it alternately with anhydrous ethanol and deionized water, and then vacuum dry it at a drying temperature of 60℃ and a drying time of 10 h to obtain ZIF-67@CoNi-LDH-BS with a complete hollow structure on a nanosheet surface.
[0077] To verify the material composition of the obtained ZIF-67@CoNi-LDH-BS material, XRD tests were performed. The results are as follows: Figure 3 As shown, only the diffraction peak of CoNi-LDH was observed in ZIF-67@CoNi-LDH-BS, indicating that ZIF-67 was completely etched after the sulfidation treatment. The test results show that the sulfidation treatment further activated the redox reaction between the multi-metal components, causing some metal ions to combine with sulfur ions.
[0078] To verify the microstructure of ZIF-67@CoNi-LDH-BS, SEM measurements were performed. The results are as follows: Figure 6a As shown, through further sulfidation treatment, a large number of nanosheets were formed on the surface of ZIF-67@CoNi-LDH-BS material. From the morphology, these ultrathin small-sized nanosheets can provide the material with a larger specific surface area, which is expected to further improve the electrochemical performance.
[0079] To further verify the structural composition of ZIF-67@CoNi-LDH-BS, TEM tests were performed. The results are as follows: Figure 6b As shown, ZIF-67@CoNi-LDH-BS exhibits a hollow nanocage structure, consistent with XRD results, confirming that ZIF-67 has been completely etched. This unique structure shortens the transport path and promotes redox kinetics.
[0080] To verify the elemental composition and distribution of ZIF-67@CoNi-LDH-BS, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) was performed. The results are as follows: Figure 7 As shown, the sample contains Co, Ni, C, O, B and S elements, and the distribution is relatively uniform, confirming the successful synthesis of ZIF-67@CoNi-LDH-BS.
[0081] To further verify the composition of ZIF-67@CoNi-LDH-BS, XPS testing was performed. The test results are as follows: Figure 8a As shown, ZIF-67@CoNi-LDH-BS contains characteristic peaks of Ni, Co, B, S, O, and C;
[0082] The test results for Co element are as follows: Figure 8b As shown, the characteristic peak of Co 2p3 / 2 undergoes a further negative shift after the second sulfidation treatment, and the fitted peak at 778.7 eV indicates that the high-valence Co is reduced to the more stable low-valence metallic Co.
[0083] Ni element test results are as follows Figure 8c As shown, the characteristic peak of Ni 2p3 / 2 shifts positively after the second sulfidation treatment, and some low-valence Ni... 2+ It was oxidized into Ni, which has higher stability and stronger electrochemical performance. 3+ ;
[0084] The test results for element O are as follows: Figure 8d As shown, the O 1s spectrum can be fitted with three peaks: lattice oxygen (OI, 530.7 eV), oxygen vacancies (OII, 531.5 eV), and chemisorbed or dissociated oxygen or OH species (OIII, approximately 532.5 eV). The OII peak intensity in the sample is significantly increased, indicating an increase in oxygen vacancies during the redox process. The lack of oxygen generates a large number of vacancies and defects, which facilitates electron transfer;
[0085] The test results for element S are as follows: Figure 8eAs shown, the peak at 168.2 eV corresponds to SO bonds, and the peaks at 162.7 eV and 161.6 eV correspond to metal-S bonds, indicating that S effectively fills oxygen vacancies.
[0086] The test results for element B are as follows: Figure 8f As shown, the peak at 186.1 eV indicates that Na₂S reduces oxidized boron to form boron atoms. Due to their small atomic size, boron atoms tend to occupy vacancies and bond with the metal. This complex metal-boron (MB) bond formation exhibits excellent oxidation resistance, which is beneficial for improving the electrochemical performance of the material.
[0087] XPS test results show that the oxidation process of room temperature sulfidation treatment with Na2S enhances the oxidizing power of the sample, which is beneficial to improving electrochemical performance.
[0088] To demonstrate the electrochemical performance of ZIF-67@CoNi-LDH-BS, electrochemical performance tests were conducted.
[0089] The cyclic voltammetry test results of ZIF-67@CoNi-LDH-BS are as follows: Figure 9 As shown, at 5 mV s -1 The test results show that, compared with the ZIF-67@CoNi-LDH-B obtained in step 3, the area enclosed by the cyclic voltammetry test curve of ZIF-67@CoNi-LDH-BS is further increased, indicating that the specific capacitance of the material is further improved.
[0090] The charge / discharge test results of ZIF-67@CoNi-LDH-BS are as follows: Figure 10 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1 A g -1 At that time, the specific capacitance of ZIF-67@CoNi-LDH-BS was 1606 F g. -1 The test results, compared with the ZIF-67@CoNi-LDH-B obtained in step 3, show that the specific capacitance performance can be improved by 105% through the vulcanization treatment in step 4.
[0091] The charge-discharge test results of ZIF-67@CoNi-LDH-BS at different current densities are as follows: Figure 11 As shown in Table 1, the specific capacitance of ZIF-67@CoNi-LDH-BS decreases slowly with increasing current density. Comparing the test results with those of ZIF-67@CoNi-LDH-B obtained in step 3, it can be seen that the rate performance can be further improved through the vulcanization treatment in step 4.
[0092] Table 1. Specific capacitance performance of ZIF-67@CoNi-LDH-BS at different current densities
[0093] The above tests collectively demonstrate that the hollow structure of ZIF-67@CoNi-LDH-BS obtained after borylation and sulfidation treatments can not only effectively improve the specific capacitance of the material, but also enhance its rate performance.
[0094] The cyclic stability test results of ZIF-67@CoNi-LDH-BS are as follows: Figure 12 As shown. In 10 A g -1 At a given current density, ZIF-67@CoNi-LDH-BS maintained 80% of its specific capacitance after 5000 cycles. The test results demonstrate that ZIF-67@CoNi-LDH-BS exhibits good cycling stability.
[0095] To demonstrate the effect of room temperature borosilicate treatment on the material structure and properties, Comparative Example 1 is provided. The ZIF-67@CoNi-LDH-B material after room temperature borosilicate treatment was subjected to hydrothermal sulfidation treatment to prepare ZIF-67@CoNi-LDH-BS-120℃.
[0096] Comparative Example 1
[0097] This comparative example describes a method for preparing ZIF-67@CoNi-LDH-BS based on hydrothermal vulcanization. The steps not specifically described are the same as those in Example 1, except that step 4 uses hydrothermal vulcanization instead of room temperature vulcanization. Specifically, the hydrothermal vulcanization process involves weighing 50 mg of ZIF-67@CoNi-LDH-B obtained in step 3 and dissolving it in 50 mL of anhydrous ethanol. Simultaneously, 0.625 g of thioacetamide is weighed and dissolved in 20 mL of anhydrous ethanol. The mixture is stirred for 2 minutes, then transferred to a polytetrafluoroethylene reactor and subjected to a hydrothermal reaction at 120°C for 30 minutes. Finally, the resulting product is filtered, washed, and dried to obtain hydrothermally vulcanized ZIF-67@CoNi-LDH-BS-120°C.
[0098] The XRD test results of ZIF-67@CoNi-LDH-BS at 120℃ are as follows: Figure 13a As shown, compared with the prepared ZIF-67@CoNi-LDH-B, ZIF-67@CoNi-LDH-BS-120℃ exhibits obvious new diffraction peaks at 2θ=20.3°, 22.1°, and 31.7°, corresponding to the (201), (112), and (311) crystal planes of NiCoS, respectively, and the characteristic peak intensities of LDH are weaker. Meanwhile, no diffraction peaks of ZIF-67 were observed.
[0099] The SEM test results of ZIF-67@CoNi-LDH-BS-120℃ are as follows: Figure 13b As shown, the dodecahedral structure exhibits significant shrinkage, with marked blunting and coarsening of the framework edges, and no fine nanosheets were observed on the surface. Comparing the test results with those of ZIF-67@CoNi-LDH-BS obtained in Example 1, it can be seen that room temperature vulcanization can essentially maintain the original dodecahedral framework structure of ZIF-67 and refine the microstructure of the material's surface.
[0100] The electrochemical performance test results of ZIF-67@CoNi-LDH-BS-120℃ are as follows: Figure 14 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1 A g -1 At that time, the specific capacitance of ZIF-67@CoNi-LDH-BS-120℃ was only 1034 Fg. -1 The test results, compared with those of ZIF-67@CoNi-LDH-BS obtained in Example 1, show that the specific capacitance of ZIF-67@CoNi-LDH-BS at 120℃ is 155%. The test results indicate that room temperature sulfidation treatment can significantly improve the specific capacitance performance of the electrode material compared to hydrothermal sulfidation treatment.
[0101] Comparative Example 1 demonstrates that the room temperature vulcanization process, i.e., the microstructure of the material, has a significant impact on the electrochemical performance of the material.
[0102] To demonstrate the effect of the order of room temperature borylation followed by sulfidation on the material structure and properties, Comparative Example 2 is provided, in which ZIF-67@CoNi-LDH is subjected to room temperature sulfidation only to prepare ZIF-67@CoNi-LDH-S; and Comparative Example 3 is provided, in which ZIF-67@CoNi-LDH is subjected to room temperature sulfidation first and then room temperature borylation to prepare ZIF-67@CoNi-LDH-SB.
[0103] Comparative Example 2
[0104] A method for preparing ZIF-67@CoNi-LDH-S based on room temperature vulcanization treatment. The steps not specifically described are the same as the preparation method in Example 1, except that: the ZIF-67@CoNi-LDH obtained in step 2 is subjected to room temperature vulcanization treatment in step 4 only to obtain ZIF-67@CoNi-LDH-S.
[0105] The XRD test results of ZIF-67@CoNi-LDH-S are as follows: Figure 15aAs shown, only the characteristic peaks of CoNi-LDH exist in ZIF-67@CoNi-LDH-S, and no peaks similar to those of S are observed. 2- Characteristic peaks related to ZIF-67.
[0106] The SEM test results of ZIF-67@CoNi-LDH-S are as follows: Figure 15b As shown, the ZIF-67@CoNi-LDH-S sheet structure disappeared and showed severe aggregation, with the dodecahedral structure collapsing. Test results indicate that direct room-temperature vulcanization of ZIF-67@CoNi-LDH destroys the dodecahedral framework and the microstructure of the surface nanosheets.
[0107] The electrochemical performance test results of ZIF-67@CoNi-LDH-S are as follows: Figure 16 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1 A g -1 At that time, the specific capacitance of ZIF-67@CoNi-LDH-S was only 1148 F g. -1 The test results, compared with those of ZIF-67@CoNi-LDH-B obtained in Example 1, show that the specific capacitance of ZIF-67@CoNi-LDH-B is 132% of that of ZIF-67@CoNi-LDH-S. The test results indicate that the first-step room temperature borylation treatment significantly improves the specific capacitance performance of the electrode material compared to the room temperature sulfidation treatment.
[0108] Comparative Example 2 demonstrates that the first step of room temperature vulcanization significantly affects the microstructure and electrochemical properties of the material.
[0109] Comparative Example 3
[0110] A method for preparing ZIF-67@CoNi-LDH-SB based on a two-step process of room temperature sulfidation and boronization is provided. The steps not specifically described are the same as the preparation method in Example 1, except that the ZIF-67@CoNi-LDH obtained in step 2 is first subjected to the sulfidation treatment in step 4, and then subjected to the boronization treatment in step 3 to obtain ZIF-67@CoNi-LDH-SB.
[0111] The XRD test results of ZIF-67@CoNi-LDH-SB are as follows: Figure 17a As shown, the diffraction peaks of ZIF-67@CoNi-LDH-SB are basically consistent with those of ZIF-67@CoNi-LDH-S.
[0112] The SEM test results of ZIF-67@CoNi-LDH-SB are as follows: Figure 17bAs shown, ZIF-67@CoNi-LDH-SB still suffers from the problem of dodecahedral structure collapse.
[0113] The electrochemical performance test results of ZIF-67@CoNi-LDH-SB are as follows: Figure 18 As shown, charging and discharging within the range of 0-0.5V, at a current density of 1 A g -1 At that time, the specific capacitance of ZIF-67@CoNi-LDH-SB was only 1348 F g. -1 The test results, compared with those of ZIF-67@CoNi-LDH-BS obtained in Example 1, show that the specific capacitance of ZIF-67@CoNi-LDH-BS is 119% of that of ZIF-67@CoNi-LDH-S. The test results indicate that the room temperature borylation-sulfidation two-step treatment process can significantly improve the specific capacitance performance of the electrode material.
[0114] Comparative Example 3 demonstrates that the overall structure of the material is directly damaged during the first step of room temperature vulcanization, resulting in structural collapse and the inability to maintain the original structural morphology. Subsequent room temperature borosilicate treatment still suffers from the problem of dodecahedral structural collapse. In other words, changing the order of borosilicate and vulcanization treatments directly affects the microstructure of the composite material.
[0115] Therefore, it can be seen that by activating the material through a two-step process of room temperature borylation and sulfidation, the core-shell structure can be transformed into a complete hollow structure while maintaining the original framework structure to a large extent, and the surface can be further refined, thereby enabling the electrode material to exhibit excellent specific capacitance and rate performance.
Claims
1. A ZIF-67 derived hollow material, characterized in that: The ZIF-67-derived hollow material is ZIF67@CoNi-LDH-BS, which has a dodecahedral hollow structure with a size of 600 nm and nanosheets distributed on its surface.
2. A two-step preparation method for the ZIF-67-derived hollow material at room temperature via borylation and sulfidation as described in claim 1, characterized in that, Includes the following steps: Step 1, preparation of ZIF-67: First, a certain mass of 2-methylimidazole is weighed and dissolved in methanol to obtain solution A; simultaneously, a certain mass of cobalt nitrate hexahydrate is weighed and dissolved in methanol to obtain solution B; then, solution A and solution B are mixed to obtain mixed solution C. After that, solution C is stirred and reacted under certain conditions and allowed to stand; finally, the obtained product is washed by centrifugation with methanol and then vacuum dried under certain conditions to obtain ZIF-67 with a smooth dodecahedral structure. Step 2, preparation of ZIF-67@CoNi-LDH: First, ZIF-67 obtained in Step 1 is dispersed in an ethanol solution at a certain mass ratio to obtain solution D; simultaneously, a certain mass of nickel nitrate hexahydrate is weighed and dissolved in an ethanol solution to obtain solution E; then, solution D and solution E are mixed to obtain mixed solution F, and then solution F is stirred and reacted under certain conditions; finally, the obtained product is washed by centrifugation with methanol and then vacuum dried under certain conditions to obtain ZIF-67@CoNi-LDH with a core-shell structure and nanosheets distributed on the surface. Step 3, Preparation of ZIF-67@CoNi-LDH-B: First, the ZIF-67@CoNi-LDH obtained in Step 2 is dispersed in deionized water at a certain mass ratio to obtain solution G; simultaneously, a certain mass of sodium borohydride is weighed and dissolved in deionized water to obtain solution H; then, solution G and solution H are mixed to obtain mixed solution I; subsequently, solution I is stirred and reacted under certain conditions; finally, the obtained product is filtered, washed alternately with anhydrous ethanol and deionized water, and then vacuum dried under certain conditions to obtain the transition state structure ZIF-67@CoNi-LDH-B with partial hollow and partial core-shell retention. Step 4, Preparation of ZIF67@CoNi-LDH-BS: First, ZIF-67@CoNi-LDH-B obtained in Step 3 is dissolved in deionized water at a certain mass ratio to obtain solution J; simultaneously, a certain mass of sodium sulfide nonahydrate is weighed and dissolved in deionized water to obtain solution K; then, solution J and solution K are mixed to obtain mixed solution L, and solution L is stirred and reacted under certain conditions; finally, the obtained product is filtered, washed alternately with anhydrous ethanol and deionized water, and then vacuum dried under certain conditions to obtain ZIF-67@CoNi-LDH-BS with a complete hollow structure on a nanosheet surface.
3. The preparation method according to claim 2, characterized in that: In step 1, the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is (1-1.5):1; the reaction temperature of the solution C under certain conditions is 20-30℃, the reaction time is 10-50 min, and the standing time is 12-36 h; the drying temperature is 50-100℃, and the drying time is 6-20 h.
4. The preparation method according to claim 2, characterized in that: In step 2, the mass ratio of ZIF-67 to nickel nitrate hexahydrate is 1:(2-2.5); the reaction temperature for stirring solution F under certain conditions is 20-30℃, and the reaction time is 60-120 min; the drying temperature is 50-100℃, and the drying time is 6-20 h.
5. The preparation method according to claim 2, characterized in that: In step 3, the mass ratio of ZIF-67@CoNi-LDH to sodium borohydride is 1:(19-21); the preparation method of the mixed solution I is as follows: solution H is added dropwise to solution G; solution I is stirred and reacted under certain conditions at a reaction temperature of 20-30℃ and a reaction time of 10-50 min; the drying temperature is 50-100℃ and the drying time is 6-20 h.
6. The preparation method according to claim 3, characterized in that: In step 4, the mass ratio of ZIF-67@CoNi-LDH-B to sodium sulfide nonahydrate is 1:(39-41); the mixed solution L is prepared by adding solution K dropwise to solution J; the reaction temperature of solution L is 20-30℃ and the reaction time is 10-50 min under certain conditions; the drying temperature is 50-100℃ and the drying time is 6-20 h.
7. The application of a ZIF-67-derived hollow material prepared by the method according to claim 3 as an electrode material for supercapacitors, characterized in that: The ZIF-67-derived hollow material ZIF-67@CoNi-LDH-BS prepared by the method was charged and discharged in the range of 0-0.5V, with a discharge current density of 1 A g. -1 At that time, the specific capacitance was 1550-1620 Fg. -1 Compared to 1 Ag -1 , in 10 A g -1 At current densities, its specific capacitance retention rate is 70-80%.