Preparation method and application of a tellurium-selenium-molybdenum sulfide catalyst

Abstract

The present invention discloses a preparation method and application of a tellurium-selenium-molybdenum sulfide catalyst, belonging to the technical field of energy materials. The preparation method comprises the following steps: S1. Adding selenium powder into a hydrazine hydrate solution to form solution A; S2. Dissolving sodium molybdate dihydrate and thiourea in a reduced graphene oxide suspension to form a mixed solution B; S3. Mixing and stirring solution A and solution B to obtain solution C, and placing solution C in an autoclave for hydrothermal reaction; S4. Washing the product obtained from the hydrothermal reaction with deionized water and freeze-drying to obtain a black product A; S5. Placing tellurium powder at the upwind of a tube furnace and product A at the downwind of the tube furnace, and performing annealing treatment in an argon-hydrogen atmosphere to obtain a tellurium-selenium-molybdenum sulfide catalyst. The present invention adopts the above-mentioned preparation method and application of a tellurium-selenium-molybdenum sulfide catalyst. The method is simple and easy to operate, and the synthesized catalyst has important practical application value in lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to a preparation method and application of a tellurium selenium molybdenum sulfide catalyst. Background Art

[0002] With the rise of the industrial revolution, industrialization, and the prosperous development of human society, fossil fuels, as the main energy source for human economic development, are facing the crisis of depletion under the continuously growing global energy demand. On the other hand, the combustion of fossil fuels and human activities have triggered a series of environmental problems, such as global warming, glacier melting, land desertification, etc. Inexpensive and clean renewable energy is an important way to solve the energy problem. Among them, lithium-ion batteries have advantages such as considerable mass energy density, no memory effect, and high open-circuit voltage, and have become one of the most important members of commercially available energy storage devices. With the growth of global demand for sustainable energy, lithium-ion batteries, as one of the main energy sources for portable electronic devices and electric vehicles, the improvement of their performance and materials has become the focus of research in the scientific field. Among them, lithium-sulfur batteries have received extensive attention due to their high energy density and low cost and have become important candidates for next-generation battery technologies. However, lithium-sulfur batteries face various challenges in practical applications, especially problems such as the solubility of polysulfides and the cycle stability of electrodes. In recent years, molybdenum disulfide (MoS2) has been considered an effective material to solve these problems due to its excellent chemical stability and catalytic performance.

[0003] Although the application of molybdenum disulfide (MoS2) in lithium-sulfur (Li-S) batteries has shown many potential advantages, such as improving the electrochemical performance of the battery, suppressing the shuttle effect of polysulfides, and enhancing catalytic activity, there are still problems such as insufficient conductivity, interface effects, and lack of catalytic properties in practical applications. These problems may limit the actual effectiveness of MoS2 and the overall performance of Li-S batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a tellurium selenium molybdenum sulfide catalyst. It is of great significance for the application of batteries to improve the electrode material with high capacity, excellent reversibility, and good cycle stability through the improved design of MoS2.

[0005] To achieve the above purpose, the present invention provides a preparation method of a tellurium selenium molybdenum sulfide catalyst, including the following steps:

[0006] S1. Add selenium powder to a hydrazine hydrate solution to form solution A;

[0007] S2. Dissolve sodium molybdate dihydrate and thiourea in a reduced graphene oxide suspension to form a mixed solution B;

[0008] S3. Mix solution A and solution B and stir to obtain solution C, and place solution C in an autoclave for hydrothermal reaction;

[0009] S4. Wash the product obtained from the hydrothermal reaction with deionized water and freeze-dry to obtain black product A;

[0010] S5. Place tellurium powder at the upwind side of a tube furnace and product A at the downwind side of the tube furnace, and perform annealing treatment in an argon-hydrogen atmosphere to obtain a tellurium-selenium-molybdenum sulfide catalyst.

[0011] Preferably, in S1, the mixing temperature of selenium powder and hydrazine hydrate is 50 - 100 °C, the purity of selenium powder > 99.99%, the particle size < 75 μm, and the hydrazine hydrate is of analytical purity.

[0012] Preferably, in S2, the purity of sodium molybdate dihydrate > 99.99%, and the concentration of reduced graphene oxide in solution B is 3 - 20 mg / mL.

[0013] Preferably, in S3, the stirring temperature is 40 - 80 °C, the stirring time is 0.25 - 3 h, the hydrothermal reaction temperature is 160 - 250 °C, and the hydrothermal reaction time is 10 - 30 h.

[0014] Preferably, in S5, the mass ratio of tellurium powder to product A is 1:2 - 0.1, the annealing temperature is 400 - 800 °C, and the time is 1 - 6 h.

[0015] Preferably, the concentrations of selenium powder, sodium molybdate dihydrate, and thiourea in solution C are all 2 - 8 mmol / mL.

[0016] Preferably, the volume percentage content of hydrazine hydrate in solution C is 10 - 50%.

[0017] Preferably, the mass percentage content of a single element of S, Se, and Te in the tellurium-selenium-molybdenum sulfide catalyst is 10 - 80%.

[0018] The present invention also provides an application of a tellurium-selenium-molybdenum sulfide catalyst. The tellurium-selenium-molybdenum sulfide catalyst prepared by the preparation method of a tellurium-selenium-molybdenum sulfide catalyst described above is used as a cathode material for preparing a lithium-sulfur battery.

[0019] Therefore, by adopting the above preparation method and application of a tellurium-selenium-molybdenum sulfide catalyst, the present invention has the following beneficial effects:

[0020] (1) The present invention combines chalcogens Te, Se, and S with Mo simultaneously to form a chalcogen catalyst with infinite solid solubility. This modification leads to the rearrangement of the electronic structure of Mo, accelerates the redox reaction of polysulfides, increases the binding energy with polysulfides, and reduces its conversion energy barrier. In addition, the introduction of different chalcogen anions forms different interlayer spacings, enhances the intrinsic conductivity, increases the ion diffusion rate, and shifts the d-band center upward, thereby reducing the occupancy of electrons in the antibonding orbitals and accelerating the conversion of polysulfides. The synthesized catalyst has important practical application value in lithium-sulfur batteries.

[0021] (2) The preparation method of the present invention obtains a molybdenum tellurium selenium sulfide catalyst grown on reduced graphene oxide through simple and mild solution treatment and hydrothermal reaction. It has a large number of defects on the surface, and the defect concentration and the ratio of tellurium, selenium, and sulfur can be controlled. By adjusting conditions such as reaction time, temperature, and the dosage of tellurium, selenium, and sulfur sources, the control of the defect concentration and the ratio of tellurium, selenium, and sulfur can be achieved.

[0022] (3) After the molybdenum tellurium selenium sulfide catalyst of the present invention is fabricated into a lithium-sulfur battery, it has a higher energy density and a longer cycle life compared to the lithium-sulfur battery prepared with molybdenum disulfide. Under the condition of 1C, the initial capacity is 990 mAh·g -1 , and the capacity retention rate after 200 cycles is about 87%. It has better application prospects in lithium-sulfur batteries.

[0023] (4) The preparation method of the molybdenum tellurium selenium sulfide catalyst of the present invention is simple and easy to operate, and does not require complex instrument equipment. Using tellurium, selenium, sulfur, and molybdenum sources as synthesis materials, it is inexpensive compared to catalyst materials containing precious metals and is suitable for industrial production.

[0024] The technical solution of the present invention will be further described in detail below through the accompanying drawings and examples. Description of the Drawings

[0025] Figure 1 is a scanning electron microscope (SEM) image of the molybdenum tellurium selenium sulfide catalyst prepared in Example 1 of the preparation method and application of a molybdenum tellurium selenium sulfide catalyst of the present invention;

[0026] Figure 2 is an elemental distribution map of the molybdenum tellurium selenium sulfide catalyst prepared in Example 1 of the preparation method and application of a molybdenum tellurium selenium sulfide catalyst of the present invention under a scanning electron microscope;

[0027] Figure 3 is the constant current charge-discharge curve of the batteries prepared with the molybdenum tellurium selenium sulfide catalyst prepared in Example 1 of the preparation method and application of a molybdenum tellurium selenium sulfide catalyst of the present invention and Comparative Example 1, Comparative Example 2, and Comparative Example 3 as the cathode material at a current of 1C. Detailed Embodiments

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains.

[0030] The present invention provides a method for preparing a tellurium-selenium-molybdenum sulfide catalyst, comprising the following steps:

[0031] S1. Add selenium powder to a hydrazine hydrate solution to form solution A; the mixing temperature of the selenium powder and hydrazine hydrate is 50 - 100 °C, the purity of the selenium powder > 99.99%, the particle size < 75 μm, and the hydrazine hydrate is of analytical grade.

[0032] S2. Dissolve sodium molybdate dihydrate and thiourea in a reduced graphene oxide suspension to form a mixed solution B; the purity of sodium molybdate dihydrate > 99.99%, and the concentration of reduced graphene oxide in solution B is 3 - 20 mg / mL.

[0033] S3. Mix solution A and solution B and stir at 40 - 80 °C for 0.25 - 3 h to obtain solution C, place solution C in an autoclave for hydrothermal reaction, the hydrothermal reaction temperature is 160 - 250 °C, and the hydrothermal reaction time is 10 - 30 h.

[0034] The concentrations of selenium powder, sodium molybdate dihydrate, and thiourea in solution C are all 2 - 8 mmol / mL, and the volume percentage content of hydrazine hydrate in solution C is 10 - 50%.

[0035] S4. Wash the product obtained from the hydrothermal reaction with deionized water and freeze-dry to obtain a black product A;

[0036] S5. Place tellurium powder at the upwind of a tube furnace and product A at the downwind of the tube furnace, the mass ratio of tellurium powder to product A is 1:2 - 0.1, perform annealing treatment in an argon-hydrogen atmosphere, the annealing temperature is 400 - 800 °C, and the time is 1 - 6 h to obtain a tellurium-selenium-molybdenum sulfide catalyst. The tellurium-selenium-molybdenum sulfide catalyst is a layered nanosheet, uniformly grown on reduced graphene oxide, with infinite solid solution and abundant defects. The ratio of S, Se, and Te in the tellurium-selenium-molybdenum sulfide catalyst is adjustable and has infinite solid solution, and the mass percentage content of a single element is 10 - 80%.

[0037] Example 1

[0038] A preparation method of a tellurium selenium molybdenum sulfide catalyst comprises the following steps: First, at 70 °C, 0.75 mmol of selenium powder is added to 2.5 mL of hydrazine hydrate solution (98%) to form solution A. Then, 0.75 mmol of sodium molybdate dihydrate and 0.75 mmol of thiourea are dissolved in 10 mL of reduced graphene oxide suspension (10 mg / mL) to form a mixed solution B. Solution A and solution B are mixed together and stirred for 15 minutes to obtain solution C. Solution C is transferred to a Teflon autoclave and stored at 200 °C for 24 hours. The product obtained from the reaction is washed with deionized water and freeze-dried to obtain a black product A. Finally, annealing treatment is carried out using a tube furnace. 3 mmol of tellurium powder is placed at the upwind side, and product A is placed at the downwind side. Annealing treatment is carried out at 550 °C in an argon-hydrogen environment for 2 hours to obtain the tellurium selenium molybdenum sulfide catalyst.

[0039] Figure 1 As shown in the scanning electron microscope (SEM) image of the tellurium selenium molybdenum sulfide catalyst prepared in Example 1, the layered MoSSeTe nanosheets prepared in Example 1 grow uniformly on the reduced graphene oxide, with an average size of about 100 nm.

[0040] Figure 2 It is the scanning electron microscope element distribution map of the tellurium selenium molybdenum sulfide catalyst prepared in Example 1. The figure shows the uniform distribution of S, Se, Te, and Mo elements on the rGO nanosheets, confirming that S, Se, and Te are successfully introduced into the tellurium selenium molybdenum sulfide catalyst.

[0041] Example 2

[0042] A preparation method of a tellurium selenium molybdenum sulfide catalyst comprises the following steps: First, at 70 °C, 1.5 mmol of selenium powder is added to 2.5 mL of hydrazine hydrate solution (98%) to form solution A. Then, 0.75 mmol of sodium molybdate dihydrate and 0.75 mmol of thiourea are dissolved in 10 mL of reduced graphene oxide suspension (10 mg / mL) to form a mixed solution B. Solution A and solution B are mixed together and stirred for 15 minutes to obtain solution C. Solution C is transferred to a Teflon autoclave and stored at 200 °C for 24 hours. The product obtained from the reaction is washed with deionized water and freeze-dried to obtain a black product A. Finally, annealing treatment is carried out using a tube furnace. 2 mmol of tellurium powder is placed at the upwind side, and product A is placed at the downwind side. Annealing treatment is carried out at 600 °C in an argon-hydrogen environment for 2 hours to obtain the tellurium selenium molybdenum sulfide catalyst.

[0043] Example 3

[0044] A preparation method of a tellurium-selenium-molybdenum sulfide catalyst includes the following steps: First, at 70 °C, 0.75 mmol of selenium powder is added to 2.5 mL of hydrazine hydrate solution (98%) to form solution A. Then, 0.75 mmol of sodium molybdate dihydrate and 1.5 mmol of thiourea are dissolved in 10 mL of reduced graphene oxide suspension (10 mg / mL) to form a mixed solution B. Solution A and solution B are mixed together and stirred for 15 minutes to obtain solution C. Solution C is transferred to a Teflon autoclave and stored at 200 °C for 24 hours. The product obtained from the reaction is washed with deionized water and freeze-dried to obtain a black product A. Finally, annealing treatment is carried out using a tube furnace. 5 mmol of tellurium powder is placed at the upwind position, and product A is placed at the downwind position. Annealing treatment is carried out at 700 °C in an argon-hydrogen environment for 2 hours to obtain the tellurium-selenium-molybdenum sulfide catalyst.

[0045] Comparative Example 1

[0046] Preparation of molybdenum disulfide catalyst: Compared with the preparation in Example 1, without solution A, the product obtained by hydrothermal treatment is annealed at 550 °C using a tube furnace under the protection of argon, and the remaining steps are the same, thus obtaining the molybdenum disulfide catalyst.

[0047] Comparative Example 2

[0048] Preparation of molybdenum diselenide catalyst: Compared with the preparation in Example 1, thiourea is not added to solution B. The product obtained by hydrothermal treatment is annealed at 550 °C using a tube furnace under the protection of argon, and the remaining steps are the same, thus obtaining the molybdenum diselenide catalyst.

[0049] Comparative Example 3

[0050] Preparation of molybdenum ditelluride catalyst: Compared with the preparation in Example 1, the selenium powder in solution A is replaced with tellurium powder of the same molar amount, thiourea is not added to solution B. The product obtained by hydrothermal treatment is annealed at 550 °C using a tube furnace under the protection of argon, and the remaining steps are the same, thus obtaining the molybdenum ditelluride catalyst.

[0051] To evaluate the effectiveness of the MoSSeTe / rGO catalyst in actual lithium-sulfur batteries, sulfur was incorporated into the samples prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 using the traditional melt impregnation method to form a sulfur cathode and fabricate it into a battery. The experimental steps are as follows: The synthesized molybdenum tellurium selenide sulfide catalyst was combined with sulfur by grinding and then heated in an inert atmosphere at 155 °C for 12 h. Subsequently, the active material (70%), polyvinylidene fluoride (PVDF, 10%), and carbon black (20%) were dissolved in N-methylpyrrolidone (NMP) to prepare a slurry. Then the slurry was coated on aluminum foil and dried in a vacuum oven at 60 °C for 12 h. The dried coated foil was cut into slices with a diameter of 10 mm. The cathodes synthesized in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1 were S@MoS2 / rGO, S@MoSe2 / rGO, S@MoTe2 / rGO, and S@MoSSeTe / rGO, respectively.

[0052] Figure 3 Performance graphs of the batteries prepared with the catalysts obtained in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1. Cyclic tests were carried out under 1C conditions. The initial discharge capacity of the S@MoSSeTe / rGO-based battery prepared in Example 1 was 990 mAh·g -1 , exceeding that of the S@MoTe2 / rGO-based battery (870 mAh·g -1 , 74.6%), the S@MoSe2 / rGO-based battery (930 mAh·g -1 ), and the S@MoS2 / rGO-based battery (835 mAh·g -1 ). This is because the incorporation of selenium and tellurium expands the layer spacing, facilitating the rapid insertion / extraction of lithium ions. In addition, the excellent conductivity and catalytic effect on polysulfides significantly accelerate the redox reaction in lithium-sulfur batteries.

[0053] Therefore, in the present invention, the above-mentioned preparation method and application of a molybdenum tellurium selenide sulfide catalyst, the molybdenum tellurium selenide sulfide catalyst, introducing Se and Te, which are both chalcogen elements, into the MoS2 / rGO composite material simultaneously will cause changes in the electronic structure of the catalyst, resulting in the upward shift of the d-band center and the decrease in the electron occupancy rate of the antibonding orbital. This modification effectively enhances the sulfur reduction reaction and can significantly improve its conversion rate by changing the conversion pathway of polysulfides. In addition, this modification expands the layer spacing and promotes the rapid movement of lithium ions. The compound prepared by this method can be infinitely solid-solved and has a stepwise catalytic effect. The lithium-sulfur battery prepared using this catalyst as the cathode material has an initial capacity of 990 mAh·g -1 under 1C conditions, and the capacity retention rate after 200 cycles is about 87%, showing great potential in lithium-sulfur batteries.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a tellurium selenium molybdenum sulfide catalyst, characterized in that: It includes the following steps: S1. Add selenium powder into hydrazine hydrate solution to form solution A; S2. Dissolve sodium molybdate dihydrate and thiourea in the reduced graphene oxide suspension to form mixed solution B; S3. Mix solution A and solution B and stir to obtain solution C, and place solution C in an autoclave for hydrothermal reaction; S4. Wash the product obtained from the hydrothermal reaction with deionized water and freeze-dry to obtain black product A; S5. Place tellurium powder at the upwind of the tubular furnace and product A at the downwind of the tubular furnace, and perform annealing treatment in an argon-hydrogen atmosphere to obtain a tellurium-selenium-molybdenum sulfide catalyst; In S5, the mass ratio of tellurium powder to product A is 1:2 - 0.1, the annealing temperature is 400 - 800 °C, and the time is 1 - 6 h.

2. The preparation method of a tellurium selenium molybdenum sulfide catalyst according to claim 1, characterized in that: In S1, the mixing temperature of selenium powder and hydrazine hydrate is 50 - 100 °C, the purity of selenium powder > 99.99%, the particle size < 75 µm, and the hydrazine hydrate is of analytical purity.

3. The preparation method of a tellurium selenium molybdenum sulfide catalyst according to claim 1, characterized in that: In S2, the purity of sodium molybdate dihydrate > 99.99%, and the concentration of reduced graphene oxide in solution B is 3 - 20 mg / mL.

4. The preparation method of a tellurium selenium molybdenum sulfide catalyst according to claim 1, characterized in that: In S3, the stirring temperature is 40 - 80 °C, the stirring time is 0.25 - 3 h, the hydrothermal reaction temperature is 160 - 250 °C, and the hydrothermal reaction time is 10 - 30 h.

5. The preparation method of a tellurium selenium molybdenum sulfide catalyst according to claim 1, characterized in that: The concentrations of selenium powder, sodium molybdate dihydrate, and thiourea in solution C are all 2 - 8 mmol / mL.

6. The preparation method of a tellurium selenium molybdenum sulfide catalyst according to claim 1, characterized in that: The volume percentage content of hydrazine hydrate in solution C is 10 - 50%.

7. Application of a tellurium-selenium-molybdenum sulfide catalyst, characterized in that: Use the tellurium-selenium-molybdenum sulfide catalyst prepared by the preparation method of a tellurium-selenium-molybdenum sulfide catalyst according to any one of claims 1 - 6 as a cathode material to prepare a lithium-sulfur battery.

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