Preparation method and application of Co3V2O8 / Co2V2O7 nanoparticle modified Co9S8 nanotube array

Abstract

The invention belongs to the technical field of composite electrode materials, and relates to a preparation method of a Co3V2O8 / Co2V2O7 nanoparticle modified Co9S8 nanotube array, which comprises the following steps: immersing dry pretreated carbon cloth in a mixed solution of a cobalt source and 2-methylimidazole, standing at 60 DEG C for 2-6 hours, and drying to obtain Co-MOF (at) CC; reacting the Co-MOF coated CC with a sulfur source at 120-200 DEG C for 4-8 hours, and drying at 60 DEG C overnight to obtain Co9S8 coated CC; and finally, immersing the Co9S8 coated CC into an NH4VO3 solution, soaking in a water bath at 80 DEG C for 0.5-1.5 hours, and washing and drying to obtain Co3V2O8 / Co2V2O7 / Co9S8 coated CC. The invention also discloses application of the prepared material to a positive electrode of a supercapacitor. The electrode material is endowed with obvious flexibility by taking the carbon cloth as a substrate, self-supporting performance is provided by combining with an in-situ growth technology, structural collapse in an electrochemical reaction process is effectively relieved, and finally, the electrode material modified by Co3V2O8 / Co2V2O7 has a heterostructure in which nanoparticles grow on the surface of a nanotube, so that the electrochemical performance of the electrode material is improved. The unique combination of the two structures significantly increases active sites, so that the electrochemical performance of the electrode material is improved, the energy consumption is low, and large-scale production is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of composite electrode materials technology, and relates to flexible self-supporting electrodes, particularly to a method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles and its application. Background Technology

[0002] With the ever-increasing global demand for portable electronic products and flexible devices, the development and application of high-performance flexible supercapacitors have gradually become a hot topic in the energy storage field. Compared with batteries, supercapacitors have advantages such as ultra-fast charging capability, superior power density, and excellent cycle stability. However, their relatively low energy density remains a key challenge for practical applications. Achieving supercapacitors with high energy density while maintaining excellent power density and ultra-long lifespan mainly depends on the research of high-performance electrode materials. Therefore, developing novel electrode materials with high specific capacity, lightweight, and mechanical stability is a challenging task that urgently needs to be accomplished.

[0003] Transition metal sulfides (TMSs) are well-known for their high theoretical capacity, abundant redox sites, and excellent electrochemical reversibility, making them highly attractive pseudocapacitive materials. However, they suffer from slow ion diffusion kinetics, limited conductivity, and structural degradation during long-cycle periods, primarily caused by volume expansion and aggregation. Therefore, constructing multi-metallic composites with heterogeneous structures is a reasonable solution. On the other hand, among numerous transition metal oxides (TMOs), cobalt-based vanadates have attracted widespread attention due to their higher electrochemical activity, conductivity, and capacity compared to single-metal oxides, thanks to the synergistic effect between cobalt and vanadium and their multiple redox sites. Furthermore, vanadium-based materials exhibit relatively low volume changes compared to other metal oxides, effectively mitigating volume changes caused by ion insertion and extraction during charge and discharge. Despite their excellent electrochemical performance, previous reports have primarily described their synthesis using cumbersome and energy-intensive multi-step methods, hindering large-scale production. Therefore, a one-step synthesis of cobalt-based vanadates would be more advantageous.

[0004] Carbon cloth (CC), woven from carbon fibers, possesses advantages such as non-toxicity, low cost, high conductivity, excellent mechanical flexibility, and structural stability. These advantages make CC an excellent substrate material for flexible supercapacitor applications. On the other hand, an electrode material that directly grows various nanostructures on a conductive substrate not only simplifies electrode fabrication but also offers significant advantages. Therefore, designing electrodes that directly grow various nanostructures on carbon cloth substrates can effectively solve the problems of poor conductivity, insufficient mechanical stability, and complex processes associated with traditional electrode materials, and is of great significance for the development of high-performance, lightweight flexible supercapacitors. Summary of the Invention

[0005] To address the problems existing in the prior art, one objective of this invention is to disclose a method for preparing Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube arrays and its application.

[0006] Technical solution

[0007] First, Co-MOF@CC was obtained by impregnating CC with cobalt salt and 2-methylimidazole (C4H6N2, 2-MIM) as raw materials. Then, Co9S8@CC was obtained by introducing a sulfur source and reacting with NH4VO3 solution. Finally, Co3V2O8 / Co2V2O7 / Co9S8@CC material was obtained by reacting with NH4VO3 solution in a water bath.

[0008] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array (Co3V2O8 / Co2V2O7 / Co9S8@CC) includes the following steps:

[0009] A. Mix 0.05M cobalt salt solution with an equal volume of 0.4M 2-MIM solution and sonicate until homogeneous. Add dried pretreated CC and soak at 60℃ for 2-6 h, preferably 4 h. After soaking, allow to cool naturally to room temperature, rinse the product with deionized water to remove residual solution and impurities, and dry at 60℃ to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0010] B. Add Co-MOF@CC to a polytetrafluoroethylene-lined autoclave containing a 0.05M sulfur source ethanol solution and react at 120~200℃ for 4~8h, preferably at 160℃ for 6h. After the autoclave has cooled naturally to room temperature, rinse it several times with anhydrous ethanol and deionized water, and dry it overnight at 60℃ to obtain Co9S8@CC.

[0011] C. Immerse Co9S8@CC in NH4VO3 solution and bathe in an 80℃ water bath for 0.5~1.5h, preferably 1h. After the solution cools naturally to room temperature, wash with anhydrous ethanol and deionized water, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0012] In a preferred embodiment of the present invention, in step A, the cobalt salt is Co(NO3)2 or CoCl2, preferably Co(NO3)2.

[0013] In a preferred embodiment of the present invention, in step A, the pretreated CC is cleaned by ultrasonic cleaning with acetone, ethanol and deionized water in sequence, and then dried for later use.

[0014] In a preferred embodiment of the present invention, in step B, the sulfur source is thioacetamide (C2H5NS, TAA) or thiourea (CH4N2S, TU), with thioacetamide being preferred.

[0015] In a preferred embodiment of the present invention, in step B, the 0.05 M sulfur source ethanol solution is prepared by dissolving the sulfur source in an ethanol solvent.

[0016] In a preferred embodiment of the present invention, in step C, the NH4VO3 solution is a 20 mL solution prepared by dissolving 0.090 g of NH4VO3 in 19 mL of deionized water and 1 mL of NH3·H2O.

[0017] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared by the method described in this invention exhibits a composite structure at the microscopic level in which Co3V2O8 / Co2V2O7 nanoparticles are attached to the surface of a neatly arranged Co9S8 nanotube array.

[0018] Another objective of this invention is to disclose the application of the prepared Co3V2O8 / Co2V2O7 / Co9S8@CC composite material as a positive electrode material for supercapacitors.

[0019] The prepared Co3V2O8 / Co2V2O7 / Co9S8@CC composite material was used as the positive electrode of a supercapacitor. 6M KOH was used as the electrolyte. Activated carbon, acetylene black, and polyvinylidene fluoride were uniformly mixed in a mass ratio of 8:1:1, and then an appropriate amount of N-methylpyrrolidone was added dropwise. The mixture was then ground into a uniform slurry, coated onto nickel foam, and dried to serve as the negative electrode material of the supercapacitor. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed on the two-electrode system to evaluate the electrochemical performance of the prepared Co3V2O8 / Co2V2O7 / Co9S8@CC electrode material. The voltage range for CV testing was 0–0.5 V, and the scan rates were 2, 5, 10, 20, 50, and 100 mV s. -1 The voltage range for GCD testing is 0–0.5 V, and the current density is 1, 2, 3, 5, 8, and 10 A g. -1 .

[0020] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite electrode material prepared in this invention was characterized structurally and analyzed for performance using instruments such as field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), and CHI760E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.) to evaluate its electrochemical performance.

[0021] All reactants and reagents used in this invention are commercially available and of analytical grade.

[0022] Beneficial effects

[0023] This invention synthesizes a Co3V2O8 / Co2V2O7 / Co9S8@CC composite electrode material in three steps: solution impregnation, solvothermal method, and water bath heating method. Using CC as a substrate endows the electrode material with excellent flexibility, while the in-situ growth technique provides self-support, effectively mitigating structural collapse during the electrochemical reaction process. The electrode material modified with Co3V2O8 / Co2V2O7 possesses a heterogeneous structure with nanoparticles grown on the surface of nanotubes. This unique combination of the two structures significantly increases the active sites, thereby improving the material's electrochemical performance, such as specific capacity and energy density. The synthesis process is simple and energy-efficient, facilitating large-scale production. Attached Figure Description

[0024] Figure 1 Field emission scanning electron microscope (FESEM) images of the Co3V2O8 / Co2V2O7 / Co9S8@CC electrode material prepared in Example 1 at different magnifications;

[0025] Figure 2 High-resolution transmission electron microscopy image of the Co3V2O8 / Co2V2O7 / Co9S8@CC electrode material prepared in Example 1;

[0026] Figure 3 GCD curve of the Co3V2O8 / Co2V2O7 / Co9S8@CC electrode material prepared in Example 1;

[0027] Figure 4 Energy density-power density diagram of the supercapacitor assembled with the Co3V2O8 / Co2V2O7 / Co9S8@CC electrode material prepared in Example 1;

[0028] Figure 5 Cyclic stability diagram of the supercapacitor assembled with the Co3V2O8 / Co2V2O7 / Co9S8@CC electrode material prepared in Example 1. Detailed Implementation

[0029] The present invention will now be described in detail with reference to embodiments to enable those skilled in the art to better understand the invention, but the invention is not limited to the following embodiments. Unless otherwise specified, the terminology used herein (including technical terms) shall be interpreted as having the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will also be understood that the terminology used herein shall be interpreted as having the same meaning as it has in the context of this specification and related art, and shall not be interpreted in an idealized or excessive manner unless specifically limited herein.

[0030] Example 1

[0031] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0032] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4h, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on carbon cloth (CC);

[0033] Step 2: Add 0.038g TAA to 10 mL of ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25 mL polytetrafluoroethylene-lined autoclave and react at 160℃ for 6 hours. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0034] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0035] Characterization and analysis of Co3V2O8 / Co2V2O7 / Co9S8@CC composite material

[0036] like Figure 1 As shown, under microscopic conditions, Co3V2O8 / Co2V2O7 / Co9S8@CC forms a unique composite structure of nanoparticles grown on the surface of a neatly arranged nanotube array, which significantly increases the number of active sites.

[0037] like Figure 2 As shown, characteristic lattice fringes corresponding to the (311) and (440) crystal planes of Co9S8, (111) crystal plane of Co2V2O7, and (122) crystal plane of Co3V2O8 can be observed from the HRTEM image, proving the successful preparation of the Co3V2O8 / Co2V2O7 / Co9S8@CC composite material.

[0038] like Figure 3 As shown in the figure, the GCD curve of the Co3V2O8 / Co2V2O7 / Co9S8@CC composite material can be seen. The calculated values ​​of this material at 1 A g are... -1 It has 1242.0 F g at that time. -1 High specific capacity.

[0039] like Figure 4 As shown, the Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment is used as the positive electrode of a supercapacitor in a two-electrode system. The energy density-power density diagram shows that the assembled supercapacitor exhibits excellent power density and energy density, with a power density of 800 W / kg. -1 The maximum energy density is 68.7 Wh / kg. -1 .

[0040] like Figure 5 As shown, the Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode of a supercapacitor for a cycle stability test. After 10,000 cycles, its specific capacitance remained at 90.6% of the initial capacity, demonstrating excellent cycle stability.

[0041] Example 2

[0042] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0043] Step 1: Clean the CC with acetone, ethanol, and deionized water in sequence using ultrasonic cleaning, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonic cleaning to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 2 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0044] Step 2: Add 0.038 g TAA to 10 mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25 mL polytetrafluoroethylene-lined autoclave and react at 160 °C for 6 h. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60 °C overnight to obtain Co9S8@CC.

[0045] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0046] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 82.1% of the initial capacitance.

[0047] Example 3

[0048] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0049] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 6h, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on carbon cloth (CC);

[0050] Step 2: Add 0.038g TAA to 10mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL polytetrafluoroethylene-lined autoclave and react at 160℃ for 6 h. After natural cooling at room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0051] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0052] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 85.6% of the initial capacitance.

[0053] Example 4

[0054] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0055] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.476g CoCl2·6H2O in 40mL deionized water by ultrasonication to form a uniform transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on carbon cloth (CC);

[0056] Step 2: Add 0.038g TAA to 10 mL of ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL polytetrafluoroethylene-lined autoclave and react at 160℃ for 6 h. After natural cooling at room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0057] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1 h, allow the beaker to cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0058] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 80.3% of the initial capacitance.

[0059] Example 5

[0060] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0061] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4h, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0062] Step 2: Add 0.038g TAA to 10mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL polytetrafluoroethylene-lined autoclave and react at 120℃ for 4h. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0063] Step 3: Weigh 0.090g NH4VO3, add 19 mL of deionized water and 1 mL of ammonia, and sonicate to form a colorless and transparent homogeneous solution. Then, immerse Co9S8@CC in the solution and heat in an 80℃ water bath for 1 h. After the beaker cools naturally at room temperature, wash it several times with deionized water and anhydrous ethanol, and dry it at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0064] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 72.3% of the initial capacitance.

[0065] Example 6

[0066] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0067] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0068] Step 2: Add 0.038g TAA to 10mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL polytetrafluoroethylene-lined autoclave and react at 120℃ for 6 h. After natural cooling at room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0069] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0070] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 77.1% of the initial capacitance.

[0071] Example 7

[0072] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0073] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0074] Step 2: Add 0.038g TAA to 10mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL polytetrafluoroethylene-lined autoclave and react at 120℃ for 8h. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0075] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0076] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 80.3% of the initial capacitance.

[0077] Example 8

[0078] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0079] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0080] Step 2: Add 0.038g TAA to 10mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL polytetrafluoroethylene-lined autoclave and react at 200℃ for 6 h. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0081] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0082] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 68.9% of the initial capacitance.

[0083] Example 9

[0084] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0085] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0086] Step 2: Add 0.038g of thiourea (TU) to 10 mL of ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25mL high-pressure reactor lined with polytetrafluoroethylene and react at 160℃ for 6 h. After natural cooling at room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60℃ overnight to obtain Co9S8@CC.

[0087] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1h, let the beaker cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0088] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 83.3% of the initial capacitance.

[0089] Example 10

[0090] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0091] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4h, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0092] Step 2: Add 0.038 g TAA to 10 mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25 mL polytetrafluoroethylene-lined autoclave and react at 160 °C for 6 h. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60 °C overnight to obtain Co9S8@CC.

[0093] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 0.5h, allow the beaker to cool naturally at room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0094] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 88.2% of the initial capacitance.

[0095] Example 11

[0096] A method for preparing a Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array includes the following steps:

[0097] Step 1: Clean the CC with acetone, ethanol and deionized water in sequence by ultrasonication, and dry it for later use; dissolve 0.582g Co(NO3)2·6H2O in 40mL of deionized water by ultrasonication to form a uniform red transparent solution, then add 2-MIM solution (1.32g 2-MIM, 40mL deionized water) and mix well. Finally, immerse the dried CC in the solution at 60℃ for 4 hours, cool it naturally to room temperature, wash it with deionized water, and dry it to obtain rod-shaped Co-MOF (Co-MOF@CC) grown on CC.

[0098] Step 2: Add 0.038 g TAA to 10 mL ethanol and sonicate to form a homogeneous solution. Then transfer the solution and Co-MOF@CC to a 25 mL polytetrafluoroethylene-lined autoclave and react at 160 °C for 6 h. After natural cooling to room temperature, wash the product with deionized water and anhydrous ethanol in sequence, and then dry at 60 °C overnight to obtain Co9S8@CC.

[0099] Step 3: Weigh 0.090g NH4VO3, add 19mL deionized water and 1mL ammonia water, sonicate to form a colorless and transparent homogeneous solution, then immerse Co9S8@CC in the solution, heat in an 80℃ water bath for 1.5h, allow the beaker to cool naturally to room temperature, wash several times with deionized water and anhydrous ethanol, and dry at 60℃ to obtain Co3V2O8 / Co2V2O7 / Co9S8@CC.

[0100] The Co3V2O8 / Co2V2O7 / Co9S8@CC composite material prepared in this embodiment was used as the positive electrode to assemble a supercapacitor. The results of the cycle stability test showed that after 10,000 cycles, its specific capacitance remained at 80.5% of the initial capacitance.

[0101] Comparative Examples 1-3: When the soaking time in step 1 is 4 hours, the cycle stability is optimal (90.6%), indicating that 4 hours is the best time for Co-MOF growth.

[0102] Comparing Examples 1 and 4: Co(NO3)2 showed better performance than CoCl2 when used as the cobalt salt, confirming that Co(NO3)2 is the preferred cobalt salt.

[0103] Comparative Examples 1 and 5-8: The best cycle stability was achieved at a solvothermal reaction temperature of 160°C and a time of 6 hours. Excessively high or low temperatures / times led to a decrease in performance.

[0104] Comparing Examples 1 and 9: TAA is superior to thiourea when used as the sulfur source, confirming that TAA is the preferred sulfur source.

[0105] Comparing Examples 1, 10, and 11: the performance was optimal when the water bath time was 1 hour; too short or too long a water bath time was detrimental to structural stability.

[0106] The embodiments described above are merely examples of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a Co9S8 nanotube array modified with Co3V2O8 / Co2V2O7 nanoparticles, characterized in that, Includes the following steps: A. Mix 0.05M cobalt salt solution with an equal volume of 0.4M 2-MIM solution and sonicate until homogeneous. Add dried pretreated CC and soak at 60℃ for 2-6 hours, preferably 4 hours. After soaking, allow to cool naturally to room temperature, rinse the product with deionized water to remove residual solution and impurities, and dry at 60℃ to obtain rod-shaped Co-MOF grown on CC, i.e., Co-MOF@CC. B. Add Co-MOF@CC to a polytetrafluoroethylene-lined autoclave containing a 0.05M sulfur source ethanol solution and react at 120~200℃ for 4~8h, preferably at 160℃ for 6h. After the autoclave has cooled naturally to room temperature, rinse it several times with anhydrous ethanol and deionized water, and dry it overnight at 60℃ to obtain Co9S8@CC. C. Immerse Co9S8@CC in NH4VO3 solution and bathe in an 80℃ water bath for 0.5~1.5h, preferably 1h. After the solution cools naturally to room temperature, wash with anhydrous ethanol and deionized water, and dry at 60℃ to obtain the final product.

2. The method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles according to claim 1, characterized in that, In step A, the cobalt salt is Co(NO3)2 or CoCl2.

3. The method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles according to claim 1, characterized in that, In step A, the cobalt salt is Co(NO3)2.

4. The method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles according to claim 1, characterized in that, In step B, the sulfur source is thioacetamide or thiourea.

5. The method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles according to claim 1, characterized in that, In step B, the sulfur source is thioacetamide.

6. The method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles according to claim 1, characterized in that, In step B, the 0.05M sulfur source ethanol solution is prepared by dissolving the sulfur source in ethanol solvent.

7. The method for preparing Co9S8 nanotube arrays modified with Co3V2O8 / Co2V2O7 nanoparticles according to claim 1, characterized in that, In step C, the NH4VO3 solution is a 20 mL solution prepared by dissolving 0.090 g of NH4VO3 in 19 mL of deionized water and 1 mL of NH3·H2O.

8. The Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array prepared by any one of the methods described in claims 1-7.

9. The Co3V2O8 / Co2V2O7 nanoparticle-modified Co9S8 nanotube array according to claim 8, characterized in that: Under microscopic conditions, a composite structure can be observed where Co3V2O8 / Co2V2O7 nanoparticles are attached to the surface of a neatly arranged array of Co9S8 nanotubes.

10. An application of the nanotube array as described in claim 8 or 9, characterized in that, It is applied to electrode materials, especially to the positive electrode materials of supercapacitors.

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