Foamed nickel loaded cobalt sulfide / nickel sulfide NF-CoS / NiS as well as preparation method and application thereof

Abstract

The invention discloses a foamed nickel loaded cobalt sulfide / nickel sulfide NF-CoS / NiS. The foamed nickel loaded cobalt sulfide / nickel sulfide NF-CoS / NiS is prepared by the following steps: firstly, taking foamed nickel NF as a substrate, loading cobalt hydroxide on the surface of the NF through first electrodeposition, then converting the NF into ZIF-67 through an impregnation method, then vulcanizing through thioacetamide and hydrothermal reaction, and finally loading Ni3S2 nanoparticles through second electrodeposition. The nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS can be obtained. The preparation method comprises the following steps: 1, preparing foamed nickel electro-deposition cobalt hydroxide; 2, preparation of the foamed nickel loaded cobalt hydroxide / ZIF-67; 3, cobalt hydroxide / cobalt sulfide NF-Co / CoS is loaded on the foamed nickel; and 4, preparation of the foamed nickel loaded cobalt sulfide / nickel sulfide NF-CoSX / Ni3S2. When the material is used as a supercapacitor material, charging and discharging are carried out in a voltage window range of 0-0.5 V, and when the current density is 1mA cm <-2 >, the area specific capacitance is 8-9F cm <-2 >; and when the current density is 10mA cm <-2 >, 70-80% of the initial capacity is still kept after 5000 charge-discharge cycles are carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitors, and particularly to a nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS, a preparation method thereof, and an application thereof. Background Art

[0002] Common materials in supercapacitor materials include metal-organic framework materials MOFs and transition metal sulfides. MOFs have the characteristics of high porosity and high specific surface area, so they have high energy storage capacity; in addition, the more important feature of MOFs is that there are many types of MOFs, for example, ZIF-67, UIO-66, MIL, that is, the microstructure can be adjusted. Among them, ZIF-67 has the characteristics of simple preparation method and relatively high specific surface area, which is beneficial to improving the specific capacitance performance. However, MOFs materials have problems of poor electrochemical performance. Currently, there are two common solutions: 1. Sulfurize the MOFs materials to convert them into transition metal sulfides; 2. Composite with transition metal sulfides on the MOFs materials. In addition, such materials are mainly powder materials.

[0003] Specifically, the technical solution based on the first method is to directly sulfurize ZIF-67 into CoS x to improve the specific capacitance of MOFs materials. For example, the existing literature 1 (Jiang Z, Lu W, Li Z, et al. Synthesis of amorphous cobalt sulfide polyhedral nanocages for high performance supercapacitors [J]. Journal of Materials Chemistry A, 2014, 2(23): 8603-8606.) prepared CoS with a rough surface and a hollow interior by stirring a mixed solution of ZIF-67, thioacetamide and ethylene glycol. x . The electrode made of this material has a specific capacitance of 932 F g -1 at a current density of 10 A g -1 , and at 10 A g -1After 1000 charge-discharge cycles at a current density of, 88.2% of the specific capacitance is still retained. This technical solution realizes a hollow structure and uses the internal and porous structures to provide short ion / electron diffusion paths in the Faraday reaction. Moreover, the hollow cavity can effectively relieve the volume expansion during the Faraday reaction, prevent structural damage, and extend the service life. However, since this technical solution uses the hydrothermal method, it directly leads to two new technical problems: 1. The morphology of the product is uneven, which increases the resistance to ion and electron transport during the transmission process, thereby reducing the electrochemical performance; 2. Since the hydrothermal method is used, heating is necessarily required during the reaction process, which leads to the formation of aggregates, that is, the aggregation problem, and ultimately leads to a decline in the cycle performance.

[0004] Specifically, for the technical solution based on the second type of method, for example, in the existing literature 2 (Wang G, Li Y, et al. “Shipin a Bottle” design of ZIF-9@CoAl LDH hybrid compound as a high performance asymmetric supercapacitor[J]. New Journal of Chemistry, 2020, 44(18): 7528-7540.), the prepared CoAl-LDH was loaded onto the surface of the prepared ZIF-9 by the hydrothermal method to obtain ZIF-9@CoAl-LDH with a nanoflower-shaped surface loaded with nanosheets. The electrode material prepared from this material has a specific capacitance of 702 F g -1 at 1 A g -1 and still retains 71.7% of the specific capacitance after 5000 charge-discharge cycles at a current density of 10 A g -1 . This technical solution utilizes the porous structure of ZIF-9 to provide an ion transport channel, that is, to realize the rapid transport of ions in the electrolyte. At the same time, CoAl-LDH is used as an active site to improve the conductivity of the composite material, and finally realizes the promotion of charge transport, improves the efficiency of the electrochemical reaction, improves the capacitance performance and the cycle stability of the material. However, this technical solution also has the technical problems caused by the hydrothermal method mentioned above - the morphology of the obtained composite material is a flower-shaped morphology with stacked sheets. During use, this microscopic morphology has problems of local stress change and volume change, which leads to a decrease in the charge transfer ability and structural stability of the material, and ultimately leads to a decrease in the specific capacitance performance.

[0005] Based on the above analysis, first, a simple summary of the existing technology is made. The above existing technologies are respectively based on two types of technical solutions to improve the technical problems existing in MOF materials. However, since the hydrothermal method is used in both cases, there are still technical problems such as material aggregation and lack of stability of the microscopic morphology.

[0006] Furthermore, combining the above two technical solutions can further improve the specific capacitance and cycling performance of MOFs materials. For example, in the existing literature 3 (Jiaxi X, Hao G, et al. Hollow Ni 3 S 4 @Co 3 S 4 with core-satellite nano-structure derived from metal-organic framework(MOF)-on-MOF hybrids as an electrode material for supercapacitors[J]. The Royal Society of Chemistry, 2024, 53, 4479-4491.), a composite precursor based on spherical Ni-MOF loaded with dodecahedral ZIF-67 was prepared by hydrothermal method. After sulfidation treatment, a Ni 3 S 4 @Co 3 S 4 heterogeneous material with a hollow structure was successfully constructed. The electrode exhibited a high specific capacitance of 747.3 C g -1 at a current density of 1 A g -1 and showed excellent cycling stability (the capacity retention rate reached 85.4% after 5000 cycles). This technical solution first constructed a ZIF-67 heterogeneous structure on the Ni-MOF substrate to form a multi-component precursor, and then converted it into transition metal sulfides by sulfidation, obtaining the technical effect of effectively improving the charge storage capacity and structural stability of the material. However, in addition to still having the technical problems caused by the hydrothermal method, this technical solution also has new technical problems caused by combining the two technical solutions. Specifically, the microscopic morphology of ZIF-67 is a dodecahedral structure, and the microscopic morphology of Ni-MOF is spherical. Therefore, when Ni-MOF and ZIF-67 are combined by hydrothermal method, there are significant structural matching differences. This technical problem directly leads to interface contact defects during the heterogeneous growth process, resulting in uneven distribution of active components and local agglomeration phenomena.

[0007] Similarly, in the prior art, there is also the existing literature 4 (Govindasamy M, Shanthi S, Elaiyappillai E, et al. Fabrication of hierarchical NiCo 2 S 4 @CoS 2nanostructures on highlyconductive flexible carbon cloth substrate as a hybrid electrode material forsupercapacitors with enhanced electrochemical performance[J].ElectrochimicaActa,2019,293:328-337.) NiCo was prepared on highly conductive flexible carbon cloth (CC) by a two-step hydrothermal method 2 S 4 @CoS 2 electrode materials with nanostructures. The specific capacitance can reach 1565 F·g -1 at a current density of 1 A g -1 , and the capacitance retention rate is 91% after 8000 cycles. This technical solution forms a three-dimensional interconnected porous network structure on the carbon cloth substrate. The nanostructures directly grown on the conductive support not only promote better mechanical adhesion and electrical contact between the active material and the substrate, but also avoid the use of binders. At the same time, NiCo 2 S 4 has high electronic conductivity, while CoS 2 provides a good ion diffusion channel. The combination of the two improves the overall charge transfer efficiency. Although this technical solution avoids the problem of structural matching differences existing in the existing literature 3 through the carbon cloth substrate, however, due to the carbon cloth substrate, it directly leads to the repeated insertion and extraction of NiCo 2 S 4 ultrathin nanosheets and ultrathin CoS 2 nanowires on the carbon cloth substrate, resulting in deformation or shedding.

[0008] From the foregoing existing literature, it can be seen that the MOF-based composite electrode materials prepared by the hydrothermal method all have technical problems such as poor structural matching, weak interfacial binding force, and poor dynamic stability, resulting in uneven distribution of active materials and local agglomeration. The electrodeposition method can avoid the technical problems generated by the foregoing hydrothermal method. For example, the existing literature 5 (Zhong X, Liu X, Li Z, et al. Electrodeposited ultra-thin FeCo 2 O 4Nanosheets on Nickel Foam as Binder-Free Electrodes for High-Performance Supercapacitors[J]. Journal of Energy Storage, 2023, 73: 109257.) Ultra-thin FeCo was prepared by a simple one-step electrodeposition method 2 O 4 nanosheets loaded on nickel foam as a high-performance electrode material, with a specific capacitance of up to 679 F·g -1 at a current density of 1 A g -1 , and a capacitance retention rate of 92.9% after 5000 cycles. The FeCo 2 O 4 nanosheets have a rich pore structure, which not only increases the specific surface area of the material but also provides channels for the rapid diffusion and effective transport of electrolyte ions. This porous structure helps to increase the contact area between the electrode material and the electrolyte, promoting ion adsorption and desorption, thereby improving the efficiency of the electrochemical reaction. However, as the deposition time prolongs, the loading amount will gradually increase, and an excessive loading amount will form a dense structure, reducing the effective contact area between the nanosheets and hindering the diffusion and transport of electrolyte ions.

[0009] In addition, the existing literature 6 (Hu X, Liu S, Chen Y, et al. One-step electrodeposition fabrication of iron cobalt sulfide nanosheet arrays on Ni foam for high-performance asymmetric supercapacitors[J]. Ionics, 2020, 26: 2095 - 2106.) directly deposited FeCoS nanospheres on the surface of nickel foam by a simple one-step electrochemical deposition method. When the current density was 1 A g -1 , the specific capacitance was 3741.03 F g -1 , at 20 A g -1The lower cycle of 10,000 times has a capacitance retention rate of 92.84%. In this technical solution, FeCoS nanospheres are directly grown on the nickel foam substrate by electrochemical deposition. As a ternary metal sulfide, FeCoS-15 nanosheets can provide richer redox reactions due to their multiple oxidation states, thus showing higher specific capacitance and better electrochemical performance than single metal sulfides. However, due to mechanical expansion caused by excessive deposition in this technical solution, the nanosphere structure composed of FeCoS-20 nanosheet arrays undergoes severe fracture and collapse. This structural damage will further affect the diffusion of electrolyte ions in the electrode material, thereby reducing its electrochemical performance.

[0010] It can be seen from the existing literature 5 and the existing literature 6 that although the electrodeposition method for preparing electrode materials can just solve the technical problems existing in the hydrothermal method, however, the electrodeposition method is affected by deposition conditions, resulting in an excessive load, which in turn leads to the technical problem of densification of the structure of the electrode material. This problem directly leads to technical problems such as a reduction in the effective contact area, hindered ion diffusion, mechanical expansion, and structural damage, and ultimately leads to a significant reduction in electrochemical performance and cycle stability. Summary of the Invention

[0011] The purpose of the present invention is to provide a nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS, its preparation method and application. Based on the basic properties that transition metal sulfides have a relatively high theoretical specific capacitance and the dodecahedron-shaped ZIF-67 has a relatively large specific surface area,

[0012] First, by first electrodepositing cobalt hydroxide on nickel foam and then in-situ growing ZIF-67, the uniform and firm distribution of ZIF-67 on the nickel foam skeleton is realized, avoiding the problem of weak bonding force caused by the structural matching difference due to morphology in the hydrothermal method;

[0013] Then, the conductivity of ZIF-67 is improved by sulfidation;

[0014] Finally, the composite material is formed by electrodepositing Ni 3 S 2 to further solve the problem of limited specific surface area and the number of active sites of single transition metal sulfides.

[0015] In addition, using nickel foam as the substrate can also solve the problems of agglomeration and binders existing in powder materials.

[0016] In order to achieve the above-mentioned invention purpose, the technical solution adopted by the present invention is:

[0017] A nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS. First, using nickel foam NF as the substrate, cobalt hydroxide is loaded on the surface of NF by the first electrodeposition to obtain nickel foam electrodeposited cobalt hydroxide NF-Co(OH) 2 , simply referred to as NF-Co; then, it is converted into ZIF-67 by the impregnation method to obtain nickel foam supported cobalt hydroxide / ZIF-67, simply referred to as NF-Co / ZIF-67; subsequently, sulfidation is carried out through thioacetamide and hydrothermal reaction to obtain nickel foam supported cobalt hydroxide / cobalt sulfide NF-Co(OH) 2 / CoS x , simply referred to as NF-Co / CoS; finally, Ni 3 S 2 nanoparticles are loaded by the second electrodeposition, and then the nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS can be obtained, simply referred to as NF-CoS / NiS;

[0018] The microscopic morphology of the NF-Co is a flaky structure; the microscopic morphology of the NF-Co / ZIF-67 is a regular dodecahedron structure; the microscopic morphology of the NF-Co / CoS is a rougher regular dodecahedron structure; the microscopic morphology of the NF-CoS / NiS is stacked spherical nanoparticles.

[0019] A preparation method of a nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS, comprising the following steps:

[0020] Step 1, preparation of nickel foam electrodeposited cobalt hydroxide. First, cobalt nitrate hexahydrate is dissolved in deionized water to obtain electrodeposition solution A. Then, using a two-electrode system and cyclic voltammetry, with nickel foam NF as the working electrode and a Pt sheet as the counter electrode, the first electrodeposition is carried out under certain conditions. Finally, after the NF that has completed the first electrodeposition is washed with deionized water and absolute ethanol, it is vacuum dried under certain conditions to obtain nickel foam electrodeposited cobalt hydroxide NF-Co(OH) 2 , simply referred to as NF-Co;

[0021] In the said Step 1, the conditions of the first electrodeposition are that the electrodeposition potential is 5 - 7V, the scanning rate is 90 - 110mVs -1 , and the electrodeposition time is 90 - 110s;

[0022] Step 2, Preparation of nickel foam supported cobalt hydroxide / ZIF-67. First, dissolve 2-methylimidazole in deionized water to obtain an impregnation solution. Then, impregnate the NF-Co obtained in Step 1 in the impregnation solution under certain conditions. Finally, wash the impregnated NF with deionized water and absolute ethanol, and then conduct vacuum drying under certain conditions to obtain nickel foam supported cobalt hydroxide / ZIF-67, abbreviated as NF-Co / ZIF-67;

[0023] In Step 2, the impregnation conditions are as follows: the impregnation time is 23 - 25 h;

[0024] Step 3, Preparation of nickel foam supported cobalt hydroxide / cobalt sulfide NF-Co / CoS. First, dissolve thioacetamide in absolute ethanol to obtain a hydrothermal reaction solution. Then, immerse the ZIF-67 / NF obtained in Step 2 into the reaction solution under certain conditions for hydrothermal reaction. Finally, wash the reacted NF with deionized water and absolute ethanol, and then conduct vacuum drying under certain conditions to obtain nickel foam supported cobalt hydroxide / cobalt sulfide NF-Co(OH) 2 / CoS x , abbreviated as NF-Co / CoS;

[0025] In Step 3, the hydrothermal conditions are as follows: the immersion method of ZIF-67 / NF is vertical immersion, the hydrothermal temperature is 110 - 130 °C, and the hydrothermal time is 5 - 7 h;

[0026] Step 4, Preparation of nickel foam supported cobalt sulfide / nickel sulfide NF-CoS X / Ni 3 S 2 First, dissolve nickel chloride hexahydrate and thiourea in deionized water to prepare electrodeposition solution B. Then, conduct the second electrodeposition under certain conditions. Finally, wash the NF after the second electrodeposition with deionized water and absolute ethanol, and then conduct vacuum drying under certain conditions to obtain nickel foam supported cobalt sulfide / nickel sulfide NF-CoS X / Ni 3 S 2 , abbreviated as NF-CoS / NiS;

[0027] In the described preparation method, all the vacuum drying conditions are as follows: the drying temperature is 50 - 70 °C, and the drying time is 11 - 13 h.

[0028] In Step 4, the conditions for the second electrodeposition are as follows: adopt a three-electrode system and chronoamperometry method. Use the NF-Co / CoS in Step 3 as the working electrode, a Pt sheet as the counter electrode, and Hg / HgO as the reference electrode. The electrodeposition potential is -1.2 - 0.2 V, and the scanning rate is 4 - 6 mV s -1, The number of cycles is 4 - 6 times;

[0029] When nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS is used as a supercapacitor material, charge and discharge are carried out within a voltage window range of 0 - 0.5V. At a current density of 1mA cm -2 , the areal specific capacitance is 8 - 9F cm -2 ; at a current density of 10mA cm -2 , after 5000 charge and discharge cycles, 70 - 80% of the initial capacity is still retained.

[0030] The technical effects of the present invention are detected by experiments, and the specific content is as follows:

[0031] It can be known from the XRD test of the present invention that NF-CoS / NiS simultaneously has the characteristic peaks of Ni 3 S 2 , ZIF-67 and Co(OH) 2 , that is, the NF-CoS / NiS composite structure material is successfully prepared.

[0032] It can be known from the SEM test of the present invention that the micro-morphology of NF-Co is a flake structure; the micro-morphology of the NF-Co / ZIF-67 is a regular dodecahedron structure; the micro-morphology of the NF-Co / CoS remains a flake structure in the NF skeleton with a regular dodecahedron structure, however, the surface of the regular dodecahedron structure changes from smooth to rough; the micro-morphology of the NF-CoS / NiS is basically similar to that of NF-Co / CoS, but the regular dodecahedron structure existing in the flake structure of the NF skeleton is transformed into small spherical shapes.

[0033] It can be known from the EDS test of the present invention that Ni element, Co element, S element, O element and N element are evenly distributed in NF-CoS / NiS.

[0034] It can be known from the three-electrode electrochemical test of the present invention that under 3M KOH solution, charge and discharge are carried out within a window voltage range of 0 - 0.5V. At a current density of 1mA cm -2 , the areal specific capacitance of the NF-CoS / NiS composite structure material is 8 - 9F cm -2 .

[0035] It can be known from the electrochemical cycle test of the present invention that at a current density of 10mA cm -2 , after the NF-CoS / NiS composite structure material is charged and discharged 5000 cycles within a window voltage range of 0 - 0.5V, 70 - 80% of the initial specific capacitance is retained.

[0036] Therefore, the present invention has the following advantages compared with the prior art:

[0037] 1. High theoretical specific capacitance of CoS based on dodecahedron, combined with the synergistic effect of stacked spherical Ni X S and CoS dodecahedron, enables the NF-CoS / NiS composite structure material to achieve high specific capacitance performance; 3 S 2 and CoS X dodecahedron, realizing high specific capacitance performance of the NF-CoS / NiS composite structure material;

[0038] 2. Electrodeposit cobalt hydroxide on nickel foam, and then in-situ grow ZIF-67 to solve the problem of insufficient bonding force caused by structural and morphological differences; moreover, by converting ZIF-67 into CoS X , the regular dodecahedron structure of ZIF-67 is retained, while the conductivity of ZIF-67 is improved; at the same time, Ni 3 S 2 nanoparticles are loaded on CoS X to further solve the problem of limited specific surface area and number of active sites of single transition metal sulfide;

[0039] 3. By electrodeposition method, load the composite material on the conductive substrate nickel foam NF, which solves both the poor conductivity of MOFs materials and the agglomeration problem of powder materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 XRD test chart of Example 1;

[0041] Figure 2 SEM test chart of NF-Co prepared in Example 1 at 2μm;

[0042] Figure 3 SEM test chart of NF-Co / ZIF-67 prepared in Example 1 at 5μm;

[0043] Figure 4 SEM test chart of NF-Co / CoS prepared in Example 1 at 5μm;

[0044] Figure 5 SEM test chart of NF-CoS / NiS prepared in Example 1 at 2μm;

[0045] Figure 6 EDS test chart of NF-CoS / NiS prepared in Example 1:

[0046] Figure 7 Charge-discharge curve of Example 1 at a current density of 1mA cm -2 ;

[0047] Figure 8 Cycling performance chart of Example 1 after 5000 cycles;

[0048] Figure 9 XRD test pattern of NF-ZIF-67-D prepared for Comparative Example 1;

[0049] Figure 10 Charge-discharge curve of NF-ZIF-67-D prepared for Comparative Example 1 at a current density of 1 mA cm -2 ;

[0050] Figure 11 XRD test pattern of NF-NiS-D-S prepared for Comparative Example 3;

[0051] Figure 12 Charge-discharge curve of NF-NiS-D-S prepared for Comparative Example 3 at a current density of 1 mA cm -2 ;

[0052] Figure 13 XRD test pattern of NF-NiS-D-D prepared for Comparative Example 4;

[0053] Figure 14 Charge-discharge curve of NF-NiS-D-D prepared for Comparative Example 4 at a current density of 1 mA cm -2 ; Detailed implementation manners

[0054] The present invention further elaborates on the content of the present invention through examples in combination with the accompanying drawings of the specification, but it is not a limitation to the present invention.

[0055] Example 1

[0056] A preparation method of nickel foam supported cobalt sulfide / nickel sulfide NF-CoS / NiS, comprising the following steps:

[0057] Step 1, preparation of nickel foam electrodeposited cobalt hydroxide. First, dissolve 14.15 g of cobalt nitrate hexahydrate in 100 mL of deionized water to obtain electrodeposition solution A. Then, using a two-electrode system and cyclic voltammetry, with nickel foam NF as the working electrode and a Pt sheet as the counter electrode, at an electrodeposition potential of 6 V and a scanning rate of 100 mV s -1 , an electrodeposition time of 100 s, perform the first electrodeposition. Finally, after washing the NF that has completed the first electrodeposition with deionized water and absolute ethanol, perform vacuum drying at a drying temperature of 60 °C and a drying time of 12 h to obtain nickel foam electrodeposited cobalt hydroxide NF-Co(OH) 2 , simply referred to as NF-Co;

[0058] In order to prove the composition of NF-Co, XRD testing was carried out. The test results are as follows Figure 1As shown, NF-Co has the characteristic peaks of Co(OH). 2 The test results show that Co(OH) was successfully loaded on the surface of NF in Step 1. 2 .

[0059] To prove the microscopic morphology of NF-Co, SEM test was carried out. The test results are as Figure 2 shown. Combining with the XRD test results, it can be seen that flaky Co(OH) is loaded on the surface of the NF skeleton. 2 .

[0060] Step 2: Preparation of nickel foam supported cobalt hydroxide / ZIF-67. First, dissolve 3 g of 2-methylimidazole in 10 mL of deionized water to obtain an impregnation solution. Then, with an impregnation time of 24 h, immerse the NF-Co obtained in Step 1 in the impregnation solution. Finally, after washing the impregnated NF with deionized water and absolute ethanol, vacuum dry it at a drying temperature of 60 °C and a drying time of 12 h to obtain nickel foam supported cobalt hydroxide / ZIF-67, abbreviated as NF-Co / ZIF-67;

[0061] To prove the composition of NF-Co / ZIF-67, XRD test was carried out. The test results are as Figure 1 shown. NF-Co / ZIF-67 not only has the characteristic peaks of Co(OH). 2 but also has the characteristic peaks of ZIF-67. The test results show that in Step 2, part of Co(OH). 2 was converted into ZIF-67, that is, NF-Co / ZIF-67 was successfully prepared.

[0062] To prove the microscopic morphology of NF-Co / ZIF-67, SEM test was carried out. The test results are as Figure 3 shown. In the flaky structure on the NF skeleton of NF-Co / ZIF-67, a new dodecahedron structure grew. Combining with the XRD test results, it can be seen that ZIF-67 was successfully loaded on NF-Co.

[0063] Step 3: Preparation of nickel foam supported cobalt hydroxide / cobalt sulfide NF-Co / CoS. First, dissolve 0.1 g of thioacetamide in 50 mL of absolute ethanol to obtain a hydrothermal reaction solution. Then, under the conditions of a hydrothermal temperature of 120 °C and a hydrothermal time of 6 h, vertically immerse the ZIF-67 / NF obtained in Step 2 in the reaction solution for hydrothermal reaction. Finally, after washing the reacted NF with deionized water and absolute ethanol, vacuum dry it at a drying temperature of 60 °C and a drying time of 12 h to obtain nickel foam supported cobalt hydroxide / cobalt sulfide NF-Co(OH). 2 / CoS x , abbreviated as NF-Co / CoS;

[0064] To prove the composition of NF-Co / CoS, XRD tests were carried out. The test results are as Figure 1 shown, only the characteristic peaks of Co(OH) 2 exist in NF-Co / CoS. However, the characteristic peaks of ZIF-67 were not detected. The test results indicate that ZIF-67 was sulfided in step 3.

[0065] To prove the microscopic morphology of NF-Co / CoS, SEM tests were carried out. The test results are as Figure 4 shown. There is no substantial difference in the basic microscopic morphology between NF-Co / CoS and NF-Co / ZIF-67, that is, it remains as a dodecahedron structure existing in the flake structure of the NF skeleton. However, the surface of the dodecahedron structure changes from smooth to rough. Combining the XRD test results, it can be seen that NF-Co / ZIF-67 was successfully transformed into NF-Co / CoS.

[0066] To prove the electrochemical performance of NF-Co / CoS, the NF-Co / CoS obtained in step 3 was subjected to electrochemical performance tests. The specific method of the electrochemical performance test was to carry out the electrochemical performance test under a three-electrode system composed of the material to be tested as the working electrode, the Hg / HgO electrode as the reference electrode, the Pt sheet electrode as the counter electrode, and 3M KOH solution as the electrolyte.

[0067] The electrochemical performance test results of NF-Co / CoS are as Figure 7 shown. When charging and discharging in the range of 0 - 0.5V and the current density is 1mA cm -2 , the specific area capacitance of NF-Co / CoS is 3.8F cm -2 .

[0068] The cycle performance test results of NF-Co / CoS are as Figure 8 shown. Under the conditions of a current density of 10A g -1 and a cycle number of 5000 cycles, 50% of the initial specific capacitance is retained.

[0069] Step 4, preparation of nickel foam supported cobalt sulfide / nickel sulfide NF-CoS X / Ni 3 S 2 First, 0.951g of nickel chloride hexahydrate and 0.761g of thiourea were dissolved in 100mL of deionized water to prepare the electrodeposition solution B. Then, using a three-electrode system and chronoamperometry, with NF-Co / CoS in step 3 as the working electrode, the Pt sheet as the counter electrode, and Hg / HgO as the reference electrode, the electrodeposition potential was -1.2 - 0.2V, and the scanning rate was 5mV s -1With the cycle number being 5 times, the second electrodeposition is carried out. Finally, after the NF after the second electrodeposition is washed with deionized water and absolute ethanol, vacuum drying is carried out at a drying temperature of 60 °C for 12 h, and nickel foam supported cobalt sulfide / nickel sulfide NF-CoS X / Ni 3 S 2 , simply referred to as NF-CoS / NiS.

[0070] To prove the composition of NF-CoS / NiS, XRD testing is carried out. The test results are as Figure 1 shown, and only the characteristic peaks of Ni 3 S 2 exist in NF-CoS / NiS. The test results show that in step 4, not only is Ni 3 S 2 successfully electrodeposited, but also the remaining Co(OH) 2 is completely sulfided.

[0071] To prove the microscopic morphology of NF-CoS / NiS, SEM testing is carried out. The test results are as Figure 5 shown. The basic microscopic morphology of NF-CoS / NiS is similar to that of NF-Co / CoS. However, the dodecahedron structure existing in the flaky structure of the NF skeleton is transformed into small spherical shapes. Combining the test results of XRD, it can be known that the small spheres are Ni 3 S 2 , that is, NiS is loaded on NF-Co / CoS.

[0072] To further prove the composition of NF-CoS / NiS, EDS testing is carried out. The test results are as Figure 6 shown. NF-CoS / NiS contains Ni element, Co element, S element, O element and N element at the same time, and the distribution of each element is uniform.

[0073] The test results of the electrochemical performance of NF-CoS / NiS are as Figure 7 shown. Under the conditions of a charge-discharge voltage range of 0 - 0.5 V and a current density of 1 mA cm -1 , the specific area capacitance of NF-CoS / NiS is 8.3 F cm -2 . Compared with step 3, it can be seen that by electrodepositing Ni 3 S 2 in step 4, the specific area capacitance performance can be significantly improved, and the improvement amplitude is 217%.

[0074] The test results of the cycling performance of NF-CoS / NiS are as Figure 8 shown. At a current density of 10 mA cm -2, under the condition that the number of cycles is 5000, NF-CoS / NiS retains 74% of the initial specific capacitance. Comparing with Step 3, it can be seen that by electro-depositing Ni 3 S 2 nanoparticles can significantly improve the cycling performance, with an improvement amplitude of 140%.

[0075] By comparing Step 3 with Step 4, it can be proved that Ni 3 S 2 in the technical solution, specifically, Ni 3 S 2 grows on the surface of dodecahedral CoS X to form a composite structure, exposing more active sites, which is conducive to promoting ion transport and allowing more electroactive parts to participate in the Faraday redox reaction. Therefore, the specific capacitance performance of NF-CoS / NiS is enhanced.

[0076] To prove the effect of electro-depositing cobalt hydroxide, i.e., Step 1 of the preparation method, on the performance, Comparative Example 1 is provided, which is a composite material prepared by directly loading ZIF-67 on nickel foam.

[0077] Comparative Example 1

[0078] A preparation method of a composite material prepared by directly loading ZIF-67 on nickel foam. The steps not specifically described in the specific steps are the same as those of the preparation method of Example 1, except that: Steps 1, 3, and 4 are not required, and in Step 2, cobalt nitrate hexahydrate is added to the impregnation solution, and NF is directly impregnated in the impregnation solution. The material obtained in Step 2 is named NF-ZIF-67-D.

[0079] The XRD test results of NF-ZIF-67-D are as Figure 9 shown. NF-ZIF-67-D has the characteristic peaks of ZIF-67. Comparing with NF-Co / ZIF-67 obtained in Step 2 of Example 1, it can be seen that the preparation method has no substantial influence on the composition.

[0080] The electrochemical performance test results of NF-ZIF-67-D are as Figure 10 shown. During charge and discharge in the range of 0 - 0.5V, at a current density of 1mA cm -1 , the areal specific capacitance of NF-ZIF-67-D is 0.055F cm -2 . Comparing with NF-Co / ZIF-67 obtained in Step 2 of Example 1, the specific capacitance of NF-Co / ZIF-67 is 7272.73% of that of NF-ZIF-67-D. The test results show that Co(OH) is prepared by electro-deposition 2, which can significantly improve the specific capacitance performance of the composite material.

[0081] To further prove the influence of the electrodeposition method and the hydrothermal method on the performance, Comparative Example 2 and Comparative Example 3 are provided. The nickel sulfide is directly loaded on the surface of nickel foam by the electrodeposition method and the hydrothermal method respectively. Specifically, Comparative Example 2 is the composite material of nickel sulfide hydrothermally loaded on nickel foam, and Comparative Example 3 is the composite material of nickel sulfide electrodeposited on nickel foam.

[0082] Comparative Example 2

[0083] A preparation method of a composite material of Ni 3 S 2 prepared by hydrothermal method on nickel foam, comprising the following steps: vertically immersing nickel foam into the electrodeposition solution B in Step 4 of Example 1, and carrying out hydrothermal reaction under the conditions of a hydrothermal temperature of 120 °C and a hydrothermal time of 4 h. The obtained material is abbreviated as NF-NiS-D-S.

[0084] The XRD test results of NF-NiS-D-S are as Figure 11 shown. NF-NiS-D-S only has the characteristic peaks of Ni 3 S 2 .

[0085] The electrochemical performance test results of NF-NiS-D-S are as Figure 12 shown. When charging and discharging in the range of 0 - 0.5 V and at a current density of 1 mA cm -1 , the areal specific capacitance of NF-NiS-D-S is 1 F cm -2 .

[0086] Comparative Example 3

[0087] A preparation method of a composite material of Ni 3 S 2 directly electrodeposited on nickel foam, comprising the following steps: using nickel foam as the working electrode and carrying out electrodeposition under the same electrodeposition conditions as in Step 4 of Example 1. The obtained material is abbreviated as NF-NiS-D-D.

[0088] The XRD test results of NF-NiS-D-D are as Figure 13 shown. NF-NiS-D-D only has the characteristic peaks of Ni 3 S 2 . It can be seen from the comparison with Example 1 that the preparation method has no substantial influence on the composition.

[0089] The electrochemical performance test results of NF-NiS-D-D are as Figure 14 shown. When charging and discharging in the range of 0 - 0.5 V and at a current density of 1 mA cm -1When the area specific capacitance of NF-NiS-D-D is 1.4 F cm -2 . Comparing with Comparative Example 2, it can be seen that the electrodeposition method can significantly increase the area specific capacitance, with an increase of up to 40%.

[0090] From Comparative Example 2 and Comparative Example 3, it can be seen that the electrodeposition method can significantly improve the specific capacitance performance.

Claims

1. A nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS, characterized in that: Firstly, nickel foam NF was used as a substrate, and cobalt hydroxide was loaded on the surface of NF by the first electrodeposition to obtain nickel foam electrodeposited cobalt hydroxide NF-Co(OH)2, referred to as NF-Co; then, it was converted into ZIF-67 by impregnation method to obtain nickel foam loaded with cobalt hydroxide / ZIF-67, referred to as NF-Co / ZIF-67; subsequently, it was sulfided by thioacetamide and hydrothermal reaction to obtain nickel foam loaded with cobalt hydroxide / cobalt sulfide NF-Co(OH)2 / CoS x , referred to as NF-Co / CoS; finally, Ni3S2 nanoparticles are loaded by a second electrodeposition to obtain nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS, referred to as NF-CoS / NiS.

2. The nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS according to claim 1, characterized in that: The microstructure of the NF-Co is a flaky structure; the microstructure of the NF-Co / ZIF-67 is a regular dodecahedron structure; the microstructure of the NF-Co / CoS is a rougher regular dodecahedron structure; the microstructure of the NF-CoS / NiS is stacked small spherical nanoparticles.

3. A method for preparing nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS, characterized in that The following steps are involved: Step 1, preparation of nickel foam electrodeposited cobalt hydroxide, first, dissolving cobalt nitrate hexahydrate in deionized water to obtain electrodeposition solution A, then using a double electrode system and cyclic voltammetry, with nickel foam NF as a working electrode and a Pt sheet as a counter electrode, performing the first electrodeposition under certain conditions, finally, washing the NF after the first electrodeposition with deionized water and anhydrous ethanol, and then vacuum drying under certain conditions, to obtain nickel foam electrodeposited cobalt hydroxide NF-Co(OH)2, referred to as NF-Co; Step 2, preparation of nickel foam loaded with cobalt hydroxide / ZIF67, first, dissolving 2-methylimidazole in deionized water to obtain an impregnation solution, then impregnating the NF-Co obtained in step 1 in the impregnation solution under certain conditions, finally, washing the impregnated NF with deionized water and anhydrous ethanol, and then vacuum drying under certain conditions to obtain nickel foam loaded with cobalt hydroxide / ZIF-67, referred to as NF-Co / ZIF-67; Step 3, nickel foam loaded with cobalt hydroxide / cobalt sulfide NF-Co / CoS, first, dissolving thioacetamide in anhydrous ethanol to obtain a hydrothermal reaction solution, then, under certain conditions, immersing the ZIF-67 / NF obtained in step 2 in the reaction solution for hydrothermal reaction, finally, washing the NF after the reaction with deionized water and anhydrous ethanol, and then vacuum drying under certain conditions to obtain nickel foam loaded with cobalt hydroxide / cobalt sulfide NF-Co(OH)2 / CoS x , referred to as NF-Co / CoS; Step 4: nickel foam loaded with cobalt sulfide / nickel sulfide NF-CoS X / Ni3S2, firstly, nickel chloride hexahydrate and thiourea are dissolved in deionized water to prepare an electrodeposition solution B, then, a second electrodeposition is performed under certain conditions, and finally, the NF after the second electrodeposition is washed with deionized water and anhydrous ethanol, and then vacuum dried under certain conditions to obtain nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS X / Ni3S2, referred to as NF-CoS / NiS.

4. The preparation method according to claim 3, characterized in that: In step 1, the conditions for the first electrodeposition are: the electrodeposition potential is 5-7V, and the scanning rate is 90-110mV s -1 , the electrodeposition time is 90-110s.

5. The preparation method according to claim 3, characterized in that: In step 2, the immersion condition is that the immersion time is 23-25 ​​hours.

6. The preparation method according to claim 3, characterized in that: In step 3, the hydrothermal conditions are as follows: the ZIF-67 / NF is immersed vertically, the hydrothermal temperature is 110-130° C., and the hydrothermal time is 5-7 h.

7. The preparation method according to claim 3, characterized in that: In the preparation method, all vacuum drying conditions are: drying temperature is 50-70° C., and drying time is 11-13 h. In step 4, the conditions for the second electrodeposition are: using a three-electrode system and a chronoamperometry method, with the NF-Co / CoS in step 3 as the working electrode, the Pt sheet as the counter electrode, and the Hg / HgO as the reference electrode, with an electrodeposition potential of -1.2-0.2 V and a scan rate of 4-6 mV s -1 , the number of cycles is 4-6 times.

8. The nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS according to patent claim 3 is characterized in that: When used as a supercapacitor material, it can be charged and discharged in the voltage window range of 0-0.5V and at a current density of 1mA cm -2 When the area specific capacitance is 8-9F cm -2 .

9. The nickel foam loaded cobalt sulfide / nickel sulfide NF-CoS / NiS according to claim 3, characterized in that: When used as a supercapacitor material, the current density is 10 mA cm -2 When the battery is charged and discharged for 5,000 times, it still retains 70-80% of its initial capacity.

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