Array sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to an array sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material and a preparation method and application thereof. After pretreated carbon cloth is immersed into a mixed solution of a soluble molybdenum source, a sulfur source and a rare earth soluble salt, a hydrothermal reaction is adopted, and the array type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material is obtained. In the array type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material obtained by the method, the array type sulfur-rich vacancy cerium doped molybdenum disulfide nanosheet grows on the pretreated carbon cloth in situ, so that the problem of poor compatibility when the array type sulfur-rich vacancy cerium doped molybdenum disulfide nanosheet is matched with a current collector and a binder for use is solved; the problem that molybdenum disulfide is poor in conductivity and cycling stability is solved in a rare earth element doping mode, and the number and distribution of sulfur vacancies are accurately controlled by regulating and controlling the doping proportion of rare earth soluble salt.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and particularly relates to an array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] Molybdenum disulfide has a unique two-dimensional layered structure and theoretically has a high specific capacitance, showing great application potential in energy storage fields such as lithium-ion batteries and supercapacitors. Its semiconductor properties endow it with certain application prospects in optoelectronic devices. By controlling the number of layers, crystal phase, and introducing defects, its bandgap and electronic structure can be adjusted to improve its optoelectronic performance.

[0003] Currently, the commonly used preparation methods for molybdenum disulfide nanosheet electrode materials include chemical vapor deposition, hydrothermal / solvothermal method, liquid-phase exfoliation method, and mechanical exfoliation method. Chemical vapor deposition is one of the mainstream methods for preparing high-quality molybdenum disulfide nanosheets with controllable number of layers. By chemically reacting molybdenum source and sulfur source and depositing them on a substrate under high-temperature conditions, the number of layers and crystal phase can be precisely controlled. However, the equipment cost is high and it is not suitable for large-scale production. The hydrothermal / solvothermal method forms molybdenum disulfide under high temperature and high pressure, which is suitable for preparing dispersed nanostructures such as nanosheets and nanoparticles. However, the number of layers and crystal phase of the molybdenum disulfide prepared by this method are difficult to control. The liquid-phase exfoliation method uses the synergistic effect of solvent and ultrasonic waves to exfoliate molybdenum disulfide into monolayer or few-layer structures. It is easy to operate and suitable for large-scale preparation, but the number of layers is difficult to precisely control and the product uniformity is poor. The mechanical exfoliation method can prepare high-quality monolayer or few-layer molybdenum disulfide, but it is difficult to precisely control the number of layers and area by mechanical operation and is not suitable for large-scale applications. It can be seen that due to certain limitations, these methods pose certain obstacles to the practical application of molybdenum disulfide in energy storage.

[0004] In existing research, the doping modification of molybdenum disulfide mainly focuses on the selection of doping elements. Some common metal elements such as iron, cobalt, and nickel are used to dope molybdenum disulfide to improve its conductivity and electrochemical performance. The research on rare earth element-doped molybdenum disulfide is relatively less. However, rare earth elements have unique electronic structures and chemical properties, which are expected to bring new breakthroughs to the performance improvement of molybdenum disulfide. Doping can change the electronic structure and crystal structure of molybdenum disulfide, increase active sites, and improve the conductivity and reaction activity of electrode materials. However, how to precisely control the doping amount and doping position to achieve the best performance improvement remains a challenge.

[0005] First, molybdenum disulfide itself has poor conductivity, which limits its application in electrode materials. Although the doping method can improve its conductivity to a certain extent, it is still difficult to meet the requirements of high-performance electrode materials. Secondly, the cycle stability is not ideal. During the charge and discharge process, molybdenum disulfide nanosheets are prone to agglomeration and structural collapse, resulting in a decrease in the cycle stability of the electrode materials. Especially under high-current charge and discharge conditions, this problem is more serious. In addition, sulfur vacancies are one of the important factors to improve the performance of molybdenum disulfide materials, but the formation and control of sulfur vacancies are relatively difficult. Existing preparation methods are difficult to accurately control the quantity and distribution of sulfur vacancies, which affects the performance stability and repeatability of electrode materials. Moreover, the existing preparation methods of molybdenum disulfide nanosheet electrodes usually require high temperature, high pressure, special equipment and reagents. The preparation process is complex and the cost is high, which is not conducive to large-scale production and application. Finally, in practical applications, molybdenum disulfide nanosheet electrodes need to be used in combination with other materials such as current collectors and binders. However, the compatibility between molybdenum disulfide and these materials is poor, and problems such as poor interfacial contact are likely to occur, affecting the performance of the electrodes. Summary of the Invention

[0006] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides an array-type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material, its preparation method and application. The present invention uses a soluble molybdenum source, a sulfur source and a rare earth soluble salt as raw materials to obtain a mixed solution. After immersing a pretreated carbon cloth into the mixed solution, a hydrothermal reaction is carried out to obtain an array-type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material. The hydrothermal method of the present invention overcomes the problems of high temperature, high pressure, special equipment and reagents in the existing technologies. At the same time, in the array-type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material obtained by the method of the present invention, the array-type sulfur-rich vacancy cerium doped molybdenum disulfide nanosheets grow in-situ on the pretreated carbon cloth, overcoming the problem of poor compatibility when used in combination with current collectors and binders. The technical defects of poor conductivity and cycle stability of molybdenum disulfide are overcome by the method of doping rare earth elements, and by adjusting the doping ratio of the rare earth soluble salt, the quantity and distribution of sulfur vacancies are accurately controlled.

[0007] To solve the above-mentioned existing technical problems, the present invention adopts the following technical solutions:

[0008] A preparation method of an array-type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material, comprising the following steps:

[0009] Disperse a soluble molybdenum source, a sulfur source and a rare earth soluble salt in a mixed solvent to obtain a mixed solution; the sulfur source is selected from L-cysteine, thiourea or thioacetamide, and the rare earth soluble salt is selected from lanthanum nitrate, neodymium chloride or cerium nitrate hexahydrate.

[0010] Anneal the carbon cloth to introduce oxygen-containing groups on the surface of the carbon cloth, and obtain the pretreated carbon cloth.

[0011] Immerse the pretreated carbon cloth into the mixed solution, and then carry out a hydrothermal reaction. During the hydrothermal process, the defects and oxidation sites on the surface of the carbon cloth provide adsorption sites. The molybdenum source and sulfur source diffuse in the solvent, nucleate on the surface of the carbon cloth, and form an array of vertically grown molybdenum disulfide nanosheets; at the same time, after rare earth ions enter the molybdenum disulfide lattice, lattice distortion will occur due to the mismatch of ion sizes. In order to relieve the stress generated by this distortion, some atoms or ions in the lattice will deviate from their original positions, thereby forming sulfur vacancies, and obtain an array-type sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material.

[0012] Preferably, the molar ratio of the soluble molybdenum source, sulfur source and rare earth soluble salt is 1:3.2:0.01 - 0.03. Appropriate doping of rare earth elements will generate cation vacancies to balance charges. As the doping amount increases, the demand for charge compensation increases, and the vacancy concentration will also increase accordingly. The doped ions have different ionic radii from Mo 4+ 、S 2- ions, and entering the lattice will cause lattice distortion. When doped appropriately, the lattice relieves the stress generated by distortion by generating vacancy defects. Within a certain range, as the doping amount increases, the vacancy concentration will increase, but when the mechanism for generating vacancies reaches its limit or is inhibited by other factors, continuing to increase the doping amount, the vacancy concentration will no longer increase or even decrease. When the doped ions occupy too many lattice positions, it will inhibit the factors that are originally beneficial to the formation of vacancies, or cause the recombination and annihilation of lattice defects, resulting in the vacancy concentration no longer increasing or even decreasing.

[0013] Preferably, the conditions for the hydrothermal reaction are: react at 180 °C - 200 °C for 10 h - 14 h. Below 180 °C will lead to incomplete reaction; above 200 °C will lead to the decomposition of reactants and the formation of side reactants. When the time is less than 10 h, the reaction is incomplete. When the time is more than 14 h, the production cost will increase, and the reaction system is under high temperature conditions for a long time, increasing the probability of side reactions and affecting the quality and yield of the product.

[0014] Preferably, the mixed solvent is composed of deionized water and N,N-dimethylformamide, and the volume ratio of deionized water to N,N-dimethylformamide is 1:1.5 - 2. The reason for using water and DMF as solvents is that water can dissolve inorganic molybdenum sources and sulfur sources, enabling the reactants to be fully mixed and contacted in the solution, which is beneficial to the progress of the reaction; DMF is a polar aprotic solvent that can dissolve many organic molybdenum sources and sulfur-containing organic compounds with poor solubility in water, expanding the range of reactant selection, enabling some molybdenum sources and sulfur sources with special structures or properties to participate in the reaction, and providing the possibility for synthesizing molybdenum disulfide with specific properties and morphologies.

[0015] Preferably, the annealing conditions are as follows: annealing in air at 400 - 450 °C for 1 - 2 h. The purpose of annealing is to introduce oxygen-containing groups on the surface of the carbon cloth. Only by introducing oxygen-containing groups can the subsequent vertical growth of molybdenum disulfide on the carbon cloth substrate be ensured. If the carbon cloth is not annealed, the growth of molybdenum disulfide on the carbon cloth will be uneven or even non-existent. Before annealing, the carbon cloth is also cleaned to remove dust in the air on the carbon cloth, carbon cloth filaments broken during the cutting process of the carbon cloth, or grease left by finger contact.

[0016] Preferably, the molar ratio of the soluble molybdenum source to the area of the pretreated carbon cloth is 1 mol: 1 - 2 cm 2 。

[0017] The present invention also protects the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material prepared by the above preparation method.

[0018] Preferably, in the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material, with the carbon cloth as the substrate, the array-type sulfur-rich vacancy cerium-doped molybdenum disulfide nanosheets grow in situ on the substrate.

[0019] Preferably, the loading amount of the array-type sulfur-rich vacancy cerium-doped molybdenum disulfide nanosheets on the substrate is 0.8 - 1.4 mg / cm 2 。

[0020] The present invention also protects the application of the above array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material in the preparation of a negative electrode material for a supercapacitor.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. In the present invention, the pretreated carbon cloth is immersed in a mixed solution of a soluble molybdenum source, a sulfur source, and a rare earth soluble salt, and then a hydrothermal reaction is used to obtain an array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material. During the hydrothermal process, the following reactions occur:

[0023] Acidification of molybdate: Under hydrothermal conditions, the soluble molybdenum source dissolves in water to form molybdate ions (MoO 4 2- ), and is converted into molybdic acid (H 2 MoO 4 ); Na 2 MoO 4 +2H + →H 2 MoO 4 +2Na + 。

[0024] Oxidation of sulfur source to form sulfide: The mercapto group (-SH) in L-cysteine is oxidized under hydrothermal conditions at high temperature, releasing hydrogen sulfide (H 2 S) or sulfide (S 2- ): C 3 H 7 NO 2 S → C 3 H 7 NO 2 + S 2- .

[0025] Generation of MoS 2 : Molybdate or molybdic acid is reduced by H 2 S or sulfide, and finally molybdenum disulfide precipitate is formed; H 2 MoO 4 + 4H 2 S → MoS 2 + 4H 2 O + S.

[0026] Under hydrothermal conditions, soluble molybdenum source and sulfur source dissolve under high temperature and high pressure. The defects and oxidation sites on the surface of the pretreated carbon cloth provide more adsorption sites, facilitating the deposition of soluble molybdenum source and sulfur source on the surface of the pretreated carbon cloth; MoO 4 2- or H 2 MoO 4 and H 2 S or S 2- diffuse in the solution, preferentially nucleate and grow vertically on the surface of the pretreated carbon cloth through a slow crystallization process. The MoS 2 material layers are combined by van der Waals forces. Due to the layered structure of the MoS 2 material, the van der Waals forces drive the molybdenum disulfide nanosheets to grow perpendicular to the substrate direction, and the weak interlayer interaction makes the newly grown nanosheets tend to stack or be vertically arranged rather than spread parallelly, thus forming a vertical molybdenum disulfide nanosheet array. Rare earth elements have special outer layer 4f electron configurations, large ionic radii and small electronegativities. When rare earth ions enter the lattice, the lattice will be distorted due to the mismatch of ion sizes. To relieve the stress generated by this distortion, some atoms or ions in the lattice will deviate from their original positions, thus forming sulfur vacancies.

[0027] 2. The present invention improves the capacitance performance of the array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material from multiple dimensions through rare-earth element doping, introducing sulfur vacancies, and constructing an array structure. Moreover, the lattice structure of molybdenum disulfide is stabilized by rare-earth element doping and introducing sulfur vacancies, enabling it to withstand the stress generated by ion intercalation and deintercalation during charge and discharge processes. Meanwhile, the in-situ grown array structure on the pretreated carbon cloth gives the array-type sulfur-vacancy-rich cerium-doped molybdenum disulfide nanosheets a stronger binding force with the carbon cloth, further ensuring the stability of the overall structure. The array structure of the array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material of the present invention is conducive to rapid ion transport. Under high-power charge and discharge conditions, it can maintain relatively stable electrochemical performance, enabling energy storage devices to better play their roles in scenarios requiring rapid charge and discharge, and improving the response speed and overall performance of the devices. In addition, the in-situ grown nanosheet structure improves the electrolyte permeability, facilitates the fast diffusion of electrolyte ions, shortens the charge transfer path inside the electrode material, accelerates charge transfer, reduces resistance, and has excellent electrical conductivity.

[0028] 3. Due to performance limitations, the application of molybdenum disulfide materials in the prior art is restricted in the fields of high-performance electrodes and new electrochemical energy storage systems. The present invention aims to significantly increase the number of active sites of the array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material, optimize the ion diffusion channels, and increase the effective contact area between the electrode and the electrolyte through innovative means such as rare-earth element doping of molybdenum disulfide nanosheets, introducing sulfur vacancies, and constructing an array structure, thereby greatly enhancing the specific capacitance and enabling it to store more electrical energy in energy storage applications and achieve a higher energy density.

[0029] 4. During the repeated charge and discharge processes of electrochemical energy storage devices, many existing molybdenum disulfide materials are prone to problems such as structural deterioration and active material shedding, resulting in a rapid decay of the capacitance performance of molybdenum disulfide materials with an increase in the number of cycles. The present invention modifies molybdenum disulfide nanosheets through a special preparation process to form a stable structure, strengthen the binding force between the active material and the conductive substrate, reduce the agglomeration and structural collapse of the material during the charge and discharge cycle process, and thus significantly enhance the cycle stability of the array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material, ensuring that it can still maintain a high capacitance performance after multiple cycles and extending the service life of electrochemical energy storage devices. Subsequently, the problems of low capacitance performance and poor stability of molybdenum disulfide materials in the prior art are overcome, endowing molybdenum disulfide electrodes with new performance advantages and broadening their application scope. This not only opens up a new market prospect for molybdenum disulfide materials but also provides a more competitive electrode material choice for the field of electrochemical energy storage, promoting the technological upgrading and development of related industries.

[0030] 5. High-performance electrochemical energy storage devices not only require high energy density but also good power density to enable rapid charging and discharging in a short time to meet the instantaneous power demands in different application scenarios. The array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material prepared by the present invention can still maintain relatively stable electrochemical performance under high-power charging and discharging conditions by optimizing its internal structure (such as the array structure promoting rapid ion transport), effectively reducing the internal resistance, increasing the power density, realizing rapid energy storage and release, and better adapting to the requirements of modern electronic devices and electric vehicles for the rapid response ability of energy storage devices.

[0031] 6. As a material with potential application value, molybdenum disulfide has certain limitations in its application in the electrode field under traditional preparation and application methods, such as insufficiently prominent capacitance performance and poor stability. The present invention endows molybdenum disulfide nanosheets with new performance advantages through innovative preparation processes and structural designs, overcomes the defects of the prior art, thereby broadening the application scope of molybdenum disulfide materials in high-performance electrodes, new electrochemical energy storage systems and other fields, and tapping its greater potential in energy storage and conversion.

[0032] 7. The prior art prepares molybdenum disulfide by annealing treatment and then adheres molybdenum disulfide to a carbon cloth using a binder, which is not only cumbersome in operation and poor in compatibility, but also the use of the binder increases the mass transfer resistance. In the array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material of the present invention, through the pretreatment of the carbon cloth, molybdenum disulfide grows uniformly on the carbon cloth substrate, overcoming the problems of mass transfer resistance and poor compatibility caused by the combination of molybdenum disulfide and the carbon cloth substrate using a binder, and also solving the defect of cumbersome preparation steps.

[0033] 8. Traditional preparation methods have problems such as complex process flows, high energy consumption, and the use of toxic and harmful chemical reagents, which do not conform to the concepts of modern green chemistry and efficient production. Different from the preparation methods of the prior art, the present invention is committed to exploring relatively simple, scalable and environmentally friendly preparation processes. By reasonably selecting raw materials and optimizing reaction conditions, while achieving the preparation of high-performance electrode materials, the preparation cost is reduced, the impact on the environment is reduced, and the sustainable development of the electrode material preparation industry is promoted. Brief Description of the Drawings

[0034] Figure 1 Among them, (a) is the electrochemical impedance diagram of Ce-MoS in Example 1 2 and MoS in Comparative Example 1 2 ; (b) is the cycling performance diagram of Ce-MoS in Example 1 2 and MoS in Comparative Example 1 2 .

[0035] Figure 2 Among them, a-c are SEM images of Ce-MoS in Example 1 at different magnification factors; 2 d is the energy dispersive spectrum of Ce-MoS; 2 Figures e-g are the distribution maps of Mo, S, and Ce elements in Ce-MoS in Example 1; 2 h is the total spectrum of element distribution of Ce-MoS in Example 1. 2

[0036] Figure 3 For Ce-MoS in Example 1 2 and MoS in Comparative Example 1 2 are electron paramagnetic resonance diagrams.

[0037] Figure 4 Among them, (a) is the cyclic voltammogram of Ce-MoS in Example 1; 2 (b) is the galvanostatic charge-discharge diagram of Ce-MoS in Example 1. 2

[0038] Figure 5 Among them, (a) is the cyclic voltammogram of MoS in Comparative Example 1; 2 (b) is the galvanostatic charge-discharge diagram of MoS in Comparative Example 1. 2 Specific Embodiments

[0039] The specific embodiments of the present invention will be described in detail below. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0040] In the methods of the prior art, the common means for preparing molybdenum disulfide materials are as follows: dissolving soluble molybdenum sources and sulfur sources in organic solvents, stirring and reacting at 160°C to 200°C to generate molybdenum disulfide precipitates. After washing and drying multiple times, they are mixed with binders and coated on conductive substrates to form electrodes. The same as the present invention is that they all revolve around the core components of molybdenum disulfide materials and utilize the electrochemical activity inherent in molybdenum disulfide itself. The difference from the prior art is that in the prior art, molybdenum disulfide materials are first prepared, and then the molybdenum disulfide materials are mixed with binders to prepare slurries and then coated on conductive substrates to form electrodes. In the preparation process of the present application, molybdenum disulfide grows directly in situ on the carbon cloth substrate, overcoming the defects of introducing additional resistance and poor compatibility by using binders.

[0041] ​​​Using the hydrothermal synthesis method of the present invention, since it involves multiple steps such as rare earth element doping, sulfur vacancy creation, and array structure construction, it is necessary to control the experimental conditions, including the ratio of raw materials, reaction temperature, time, and the use of the templating agent N,N-dimethylformamide, which can guide the growth of molybdenum disulfide through intermolecular interactions, and has relatively high purity requirements for the raw materials of molybdenum source, sulfur source, and cerium source (all need to be of analytical purity), realizing the preparation of a high-capacitance array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material. In the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material, by introducing rare earth element doping during the synthesis process, the electronic structure of molybdenum disulfide is changed, increasing the active sites of the rare earth element-doped molybdenum disulfide nanosheets; creating sulfur vacancies can further improve the ion diffusion rate and storage capacity; constructing an array structure is beneficial to increasing the contact area between the electrode and the electrolyte, enhancing the overall performance of the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material.

[0042] For the molybdenum disulfide material prepared by the traditional method, due to the lack of doping, vacancy, and special structure design, its internal electronic structure is single and the active sites are limited, resulting in a small number of ions that can participate in electrochemical energy storage during the charge and discharge process. At the same time, the stacking mode of the molybdenum disulfide material is relatively disorderly, and the effective contact area between the electrode and the electrolyte is small, restricting the adsorption and diffusion of ions, leading to poor capacitance performance. Under the same test conditions, the specific capacitance of the molybdenum disulfide material prepared by the prior art is significantly lower than that of the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material of the present invention. For example, at a specific current density, the specific capacitance of the existing molybdenum disulfide material may only be 100 F / g, while the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material of the present invention can reach more than 472.85 F / g. Moreover, the molybdenum disulfide material prepared by the prior art solution also has problems of aggregation and structure collapse during the charge and discharge cycle. For example, after a certain number of charge and discharge cycles (such as 1000 times), the capacitance retention rate of the molybdenum disulfide material prepared by the prior art may only be 60%, while the array-type sulfur-rich vacancy rare earth element-doped molybdenum disulfide nanosheet electrode material of the present invention can reach more than 80% due to its stable structure.

[0043] The following uses examples and comparative examples to study the technical solution of the present invention, and the specific research methods and results are as follows:

[0044] Example 1

[0045] A preparation method for an array-type sulfur-rich vacancy cerium-doped molybdenum disulfide nanosheet electrode material, comprising the following steps:

[0046] S1. Take a 1×2 cm 2The CFC carbon cloth (WOS1001 from CeTech) was washed with deionized water and ethanol, dried in an oven at 60 °C, and annealed in air at 450 °C for 1 h to obtain the pretreated carbon cloth.

[0047] S2. Weigh 0.26 g of anhydrous sodium molybdate, 0.4889 g of L-cysteine, and 0.0082 g of cerium nitrate hexahydrate, and dissolve them in a mixed solvent composed of 22 mL of deionized water and 33 mL of N,N-dimethylformamide to obtain a mixed solution.

[0048] S3. Place the pretreated carbon cloth from step S1 into the mixed solution from step S2, react at 200 °C for 12 h, naturally cool to room temperature, wash the resulting product, and dry it in vacuum at 60 °C to obtain the array-type sulfur-vacancy-rich cerium-doped molybdenum disulfide nanosheet electrode material, denoted as Ce-MoS 2 .

[0049] Example 2

[0050] A preparation method of an array-type sulfur-vacancy-rich cerium-doped molybdenum disulfide nanosheet electrode material includes the following steps:

[0051] S1. Wash a 1×2 cm 2 CFC carbon cloth (WOS1001 from CeTech) with deionized water and ethanol, dry it in an oven at 60 °C, and anneal it in air at 400 °C for 2 h to obtain the pretreated carbon cloth.

[0052] S2. Weigh 0.26 g of anhydrous sodium molybdate, 0.4889 g of L-cysteine, and 0.0055 g of cerium nitrate hexahydrate, and dissolve them in a mixed solvent composed of 22 mL of deionized water and 33 mL of N,N-dimethylformamide to obtain a mixed solution.

[0053] S3. Place the pretreated carbon cloth from step S1 into the mixed solution from step S2, react at 180 °C for 14 h, naturally cool to room temperature, wash the resulting product, and dry it in vacuum at 60 °C to obtain the array-type sulfur-vacancy-rich cerium-doped molybdenum disulfide nanosheet electrode material.

[0054] Example 3

[0055] S1. Wash a 1×2 cm 2 CFC carbon cloth (WOS1001 from CeTech) with deionized water and ethanol, dry it in an oven at 60 °C, and anneal it in air at 450 °C for 1 h to obtain the pretreated carbon cloth.

[0056] S2. Weigh 0.26 g of anhydrous sodium molybdate, 0.4889 g of L-cysteine, and 0.011 g of cerium nitrate hexahydrate, and dissolve them in a mixed solvent composed of 22 mL of deionized water and 33 mL of N,N-dimethylformamide to obtain a mixed solution.

[0057] S3. Place the pretreated carbon cloth from step S1 into the mixed solution of step S2, react at 190 °C for 10 h, naturally cool to room temperature, wash the obtained product, and dry it under vacuum at 60 °C to obtain an array-type sulfur-vacancy-rich cerium-doped molybdenum disulfide nanosheet electrode material.

[0058] Comparative Example 1

[0059] The array-type molybdenum disulfide nanosheet electrode material has the same preparation steps as in Example 1, except that cerium nitrate hexahydrate is not used in the reaction, and it includes the following steps:

[0060] S1. Wash the CFC carbon cloth (WOS1001 from CeTech) with deionized water and ethanol, dry it in an oven at 60 °C, and anneal it in air at 450 °C for 1 h to obtain a pretreated carbon cloth.

[0061] S2. Weigh 0.26 g of anhydrous sodium molybdate and 0.4889 g of L-cysteine, and dissolve them in a mixed solvent composed of 22 mL of deionized water and 33 mL of N,N-dimethylformamide to obtain a mixed solution.

[0062] S3. Place the pretreated carbon cloth from step S1 into the mixed solution of step S2, react at 200 °C for 12 h, naturally cool to room temperature, wash the obtained product, and dry it under vacuum at 60 °C to obtain an array-type molybdenum disulfide nanosheet electrode material, denoted as MoS 2 .

[0063] In Examples 1 to 3 of the present invention, array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode materials with excellent electrical conductivity and cycle stability are prepared. Taking the array-type sulfur-vacancy-rich rare-earth element-doped molybdenum disulfide nanosheet electrode material of Example 1 as an example for research, the specific research methods and results are as follows:

[0064] Figure 1 (a) The results show that the intersection point of the Nyquist plot with the x-axis shifts to the left and the ohmic resistance decreases, indicating that at high frequencies, the resistance encountered when the current passes through the Ce-MoS 2 material becomes smaller, and the Ce-MoS 2 material has better electrical conductivity at high frequencies and can respond more quickly to the changes in charge and discharge currents. Figure 1 (b) The results show that after 5000 cycles, Ce-MoS 2The specific capacitance of the material can still maintain 86% of the original value. Compared with pure molybdenum disulfide, Ce-MoS 2 The cycling stability of the material has been greatly improved.

[0065] Figure 2 In [reference], a-c are SEM images of Ce-MoS 2 material at different magnifications. It can be seen that Ce-MoS 2 material grows in-situ on the pretreated carbon cloth substrate in the form of nanosheet arrays. d is the energy dispersive spectrum of Ce-MoS 2 material. Figures e-g are the elemental distribution maps of Ce-MoS 2 material. h is the total elemental distribution spectrum, proving that cerium elements are successfully incorporated.

[0066] Figure 3 For the Ce-MoS 2 material of Example 1, the electron paramagnetic resonance graph shows that the G value of sulfur vacancies is about 2.004. The intensity of the EPR signal is usually positively correlated with the concentration of vacancies. The higher the vacancy concentration, the relatively more the number of unpaired electrons, and the stronger the electromagnetic radiation signal absorbed or emitted. Through the electron paramagnetic resonance characterization of MoS 2 and Ce-MoS 2 materials, it shows that more sulfur vacancies are introduced in the Ce-MoS 2 material.

[0067] Both the cyclic voltammetry curve and the galvanostatic charge-discharge curve were tested using a three-electrode system. The test method is as follows: using a platinum wire as the counter electrode, using the MoS 2 of Comparative Example 1 or the Ce-MoS 2 material of Example 1 as the working electrode, and using a saturated calomel electrode as the reference electrode to jointly form a three-electrode system. One end of the counter electrode, reference electrode, and working electrode is jointly placed in 1 mol / L H 2 SO 4 solution, and the other end is jointly electrically connected to an electrochemical workstation.

[0068] Figure 4 The results show that the capacitance of the Ce-MoS 2 material of Example 1 is 472.85 F / g.

[0069] Figure 5 The results show that the capacitance of the MoS 2 of Comparative Example 1 is 256.57 F / g.

[0070] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations. The above-described embodiments are only preferred embodiments given to fully illustrate the present invention, and the scope of protection is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the scope of protection of the present invention, and the scope of protection of the present invention is subject to the claims.

Claims

1. A method for preparing an array-type sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material, characterized in that: The steps include: Dispersing a soluble molybdenum source, a sulfur source and a soluble rare earth salt in a mixed solvent to obtain a mixed solution; The carbon cloth is annealed to introduce oxygen-containing groups on the surface of the carbon cloth to obtain a pretreated carbon cloth; The pretreated carbon cloth is immersed in the mixed solution, and then a hydrothermal reaction is carried out. During the hydrothermal process, defects and oxidation sites on the surface of the carbon cloth provide adsorption sites, and the molybdenum source and the sulfur source diffuse in the solvent, nucleate on the surface of the carbon cloth, and form a vertically grown array of molybdenum disulfide nanosheets; at the same time, rare earth ions enter the molybdenum disulfide lattice to form sulfur vacancies, thereby obtaining an array-type sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material; Among them, the molar ratio of the soluble molybdenum source, the sulfur source and the soluble rare earth salt is 1:3.2:0.01-0.

03.

2. The method for preparing the array-type sulfur-vacancy-rich rare earth element doped molybdenum disulfide nanosheet electrode material according to claim 1, characterized in that: The rare earth soluble salt is selected from lanthanum nitrate, neodymium chloride or cerium nitrate hexahydrate.

3. The method for preparing the array-type sulfur-vacancy-rich rare earth element doped molybdenum disulfide nanosheet electrode material according to claim 1, characterized in that: The conditions of the hydrothermal reaction are: reacting at 180°C to 200°C for 10h to 14h.

4. The method for preparing an array-type sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material according to claim 1, characterized in that: The mixed solvent consists of deionized water and N,N-dimethylformamide, and the volume ratio of the deionized water to the N,N-dimethylformamide is 1:1.5-2.

5. The method for preparing array-type sulfur-vacancy-rich rare earth element doped molybdenum disulfide nanosheet electrode material according to claim 1, characterized in that: The annealing conditions are: annealing in air at 400°C to 450°C for 1h to 2h.

6. The method for preparing array-type sulfur-vacancy-rich rare earth element doped molybdenum disulfide nanosheet electrode material according to claim 1, characterized in that: The ratio of the amount of soluble molybdenum source to the area of ​​pretreated carbon cloth is 1 mol: 1 cm 2 ~2cm 2 .

7. An array-type sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. The array-type sulfur-vacancy-rich rare earth element doped molybdenum disulfide nanosheet electrode material according to claim 7, characterized in that: In the array-type sulfur-rich vacancy rare earth element doped molybdenum disulfide nanosheet electrode material, a pretreated carbon cloth is used as a substrate, and array-type sulfur-rich vacancy cerium doped molybdenum disulfide nanosheets are in-situ grown on the substrate.

9. The array-type sulfur-vacancy-rich rare earth element doped molybdenum disulfide nanosheet electrode material according to claim 8, characterized in that: The loading amount of array-type sulfur-vacancy-rich cerium-doped MoS2 nanosheets on pretreated carbon cloth is 0.8 mg / cm 2 ~1.4mg / cm 2 .

10. Use of the array-type sulfur-vacancy-rich rare earth element-doped molybdenum disulfide nanosheet electrode material according to claim 7 in preparing a supercapacitor negative electrode material.

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