CN115094438B - A one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial and its preparation method and application - Google Patents

Abstract

The invention provides a one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial and its preparation method and application. The molybdenum source and imidazole are mixed in water, and the obtained solution is heated and reacted to obtain one-dimensional nanostructure Mo -MOF; Dissolve the selenium source in hydrazine hydrate, add the obtained selenium source hydrazine hydrate solution to absolute ethanol, then add one-dimensional nanostructure Mo-MOF, stir evenly, and heat for reaction to obtain one-dimensional structure diselenide The molybdenum/molybdenum-MOF composite nanomaterial has the shape of two-dimensional structure MoSe ₂ nanosheets grown on the surface of the one-dimensional nanostructured Mo-MOF. The materials required for the preparation process of the present invention are easy to obtain and low-cost, and the experimental equipment and The operation is simple, the reaction is controllable, and it is easy to repeat. As a hydrogen evolution reaction electrocatalyst, the MoSe ₂ /Mo‑MOF composite nanomaterial prepared by the invention has excellent performance, low price, is applicable in both acidic and alkaline environments, and has good practical application value.

Description

A one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial and its preparation method and application

Technical field

The invention belongs to the field of material preparation, and specifically relates to a method for preparing a one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial, and its application as a catalyst for electrolytic water splitting and hydrogen evolution reaction in both acidic and alkaline environments.

Background technique

The continuous increase in global fossil fuel consumption has brought very serious environmental problems to people. The warming global climate is also a consequence of the long-term and extensive use of fossil fuels. In addition, fossil fuels such as coal, natural gas and oil are also facing depletion problems because they are difficult to regenerate in a short period of time. The development of efficient, clean, and renewable energy has become a top priority. Among various sustainable energy sources, hydrogen is one of the most promising candidates to replace traditional fossil fuels. Because it has a high combustion calorific value, high energy density and only produces water after combustion, it is an excellent clean energy source. energy. However, the application of hydrogen still needs to solve many problems, among which how to produce hydrogen efficiently is a bottleneck.

Electric energy generated by renewable energy sources such as solar energy and wind energy is used to electrolyze water, and hydrogen is produced through the hydrogen evolution reaction at the cathode. Pure hydrogen can be produced at the cathode. It has attracted great attention due to its many advantages such as simple and mild preparation conditions and easy availability of raw materials. However, the electrolysis of water to produce hydrogen requires efficient electrocatalysts to perform the hydrogen evolution reaction to reduce cathode overpotential, improve energy utilization efficiency, and achieve efficient and rapid hydrogen evolution reaction. The catalysts usually used are precious metals (such as Pt, Pd) that are relatively expensive and have limited reserves, which restricts the large-scale application of the electrolysis water hydrogen production process in industrial production. Therefore, it is necessary to develop materials with high catalytic ability, cheap and easily available materials as catalysts for the hydrogen evolution reaction of water electrolysis.

In recent years, scientists have discovered through research that the binding energy of the sheet edges of the transition metal selenide MoSe ₂ with a two-dimensional sheet structure and hydrogen is similar to that of noble metals, so it can replace noble metals as a hydrogen evolution reaction catalyst. However, the basal surface of the MoSe ₂ sheet has no catalytic activity, and the characteristics of the sheet structure make MoSe ₂ easy to agglomerate and aggregate, reducing the number of catalytically active edges and reducing its catalytic performance. Moreover, the performance of MoSe ₂ in catalyzing the hydrogen evolution reaction in an alkaline environment is very weak, which also hinders its practical use.

Contents of the invention

The purpose of the present invention is to solve at least one of the above technical problems. The present invention provides a one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial and a preparation method thereof. The synthesis process of MoSe ₂ nanosheets with a three-dimensional structure uses simple raw materials and process equipment and is low-cost.

Another object of the present invention is to provide a one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial, which can be used as a catalytic material for electrolytic water hydrogen evolution reaction with high catalytic performance and good performance in both acidic and alkaline environments. Good catalytic electrolysis water hydrogen evolution reaction activity.

The specific technical solutions of the present invention are as follows:

A method for preparing one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterials, including the following steps:

A. Mix the molybdenum source and imidazole in water, and the obtained solution undergoes a heating reaction to obtain a one-dimensional nanostructure Mo-MOF;

B. Dissolve the selenium source in hydrazine hydrate, add the selenium source hydrazine hydrate solution to absolute ethanol, then add the product obtained in step A, stir evenly, and heat the reaction to obtain one-dimensional structure molybdenum diselenide/molybdenum- MOF composite nanomaterials.

The mass ratio of the molybdenum source and imidazole described in step A is 1:1 to 2:1;

The molybdenum source in step A is selected from molybdenum trioxide (MoO ₃ );

In step A, the dosage ratio of the molybdenum source and water is 1:50-100g/ml;

The water mentioned in step A is deionized water;

The heating reaction described in step A refers to: reaction at 90 to 120°C for 10 to 14 hours;

Preferably, the heating reaction described in step A is: move the obtained solution into a polytetrafluoroethylene-lined reaction kettle, seal the reaction kettle, put it into a constant temperature blast box, heat the reaction, and after the reaction is completed, centrifuge to collect, and Clean and dry the product obtained in the reaction kettle; the obtained product is a one-dimensional nanostructured metal-organic framework compound (MOF) Mo-MOF formed by molybdenum ions and the organic ligand imidazole.

The selenium source in step B is selenium powder, selenium dioxide or sodium selenite; preferably, the selenium source is selenium powder;

In step B, the selenium source is dissolved in hydrazine hydrate with a concentration of 0.06 to 0.1 mol/L; the mass fraction concentration of hydrazine hydrate used is ≥85%;

In step B, the volume ratio of the selenium source hydrazine hydrate solution and absolute ethanol is 1:10 to 1:14;

In step B, the dosage ratio of the mass of the product obtained in step A and the volume of absolute ethanol is 1:1-2g/L;

The heating reaction described in step B means: reacting at 200-240°C for 10-14 hours.

The specific heating reaction described in step B is: move the resulting solution into a polytetrafluoroethylene-lined reaction kettle, seal the reaction kettle, put it into a constant temperature blast box, heat the reaction, and after the reaction is completed, centrifuge to collect the reaction kettle. The obtained product is further washed and dried to obtain the final product.

The invention provides a method for preparing a one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial, which is prepared by the above method. Two-dimensional structure MoSe ₂ nanometers are grown on the surface of the one-dimensional nanostructure Mo-MOF. The final product is a one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial composed of MoSe ₂ and Mo-MOF. The diameter of the prepared one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial is 400-900 nm, the length is 10-20 microns, and the thickness of the MoSe ₂ nanosheets on the surface of the composite material is 4-5 nm.

The application of the one-dimensional structure molybdenum diselenide/molybdenum-MOF composite nanomaterial provided by the invention is used as an electrocatalyst for the electrolysis of water and hydrogen evolution reaction, and can be used to catalyze the electrolysis of water for hydrogen evolution reaction in acidic and alkaline environments.

In recent years, a variety of hydrogen evolution reaction catalysts based on non-noble metals such as transition metal chalcogenides, nitrides, carbides, and phosphides have been studied as potential alternatives to platinum group metals. Among them, transition metal selenide is considered to be a promising hydrogen evolution reaction catalyst because of its wide distribution of resources on the earth and its good physical and chemical properties. MoSe ₂ is a transition metal selenide with a two-dimensional lamellar structure. The two-dimensional lamellae are connected through van der Waals interactions. Theoretical calculations show that the edges of MoSe ₂ two-dimensional sheets are active sites that catalyze the hydrogen evolution reaction. However, due to the structural characteristics of its two-dimensional sheet, the MoSe ₂ sheet is prone to agglomeration and aggregation, reducing the number of exposed catalytically active edges of the two-dimensional sheet, and the base surface of its two-dimensional sheet is catalytically inert. , which weakens the catalytic performance of MoSe ₂ for the hydrogen evolution reaction. Therefore, how to design and prepare a specific structure to effectively avoid the agglomeration of MoSe ₂ sheets and increase the exposure of catalytic active sites for hydrogen evolution reaction at the edges of the sheets is a problem that needs to be solved in the preparation of MoSe ₂ hydrogen evolution reaction catalysts. In addition, MoSe ₂ can exhibit significant catalytic hydrogen evolution reaction performance in acidic environments, but its catalytic performance is very weak in alkaline environments. This is because the reaction mechanisms of the electrolytic water hydrogen evolution reaction are different in acidic and alkaline environments. There are free H ⁺ ions in an acidic environment. The hydrogen evolution reaction step is mainly the interaction between the catalyst and H ⁺ ions. Because the edge of the MoSe ₂ two-dimensional sheet has good hydrogen adsorption free energy, it can show good performance in an acidic environment. Remarkable catalytic hydrogen evolution reaction performance. In an alkaline environment, the hydrogen evolution reaction process is closely related to the adsorption/dissociation process of water by the catalyst. Due to the slow adsorption/dissociation process of water by MoSe ₂ , its catalytic hydrogen evolution reaction activity in an alkaline environment is low. Therefore, how to improve the catalytic hydrogen evolution reaction performance of MoSe ₂ in an alkaline environment is one of the key issues that need to be solved for the practical application of the electrolytic water hydrogen production process.

MOF (Metal Organic Frameworks) materials are a type of porous coordination polymer materials formed by transition metal ions and organic ligands through coordination bonds. MOF materials have many excellent properties such as high porosity, large specific surface area, and adjustable pore size. They have been used in fields such as gas adsorption and separation, ion transport, and drug carriers. Due to its porous structural characteristics, MOF materials have good adsorption properties for water molecules. However, due to the lack of appropriate adsorption/desorption energy for the intermediate products of the electrocatalytic hydrogen evolution reaction, the catalytic performance of most MOF materials is severely limited, making them unable to be used as hydrogen evolution reaction catalysts.

The present invention creatively combines MoSe ₂ with catalytic activity for hydrogen evolution reaction and MOF material with water molecule adsorption performance to prepare a one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial.

In the liquid phase preparation process of micro-nano MOF materials, changes in reaction solvent, reaction temperature and time, pH value, and molar ratio of metal to ligand have a great impact on the structure, size, and morphology of the synthesized MOF materials. The reason is that the polarity of different solvents, the pH of the solution, and the difference in the solubility of the solvent to metals and organic ligands will lead to different bridging coordination modes of the central metal ion and the organic ligands, and will affect the nucleation rate of the MOF material. , oriented growth, and self-assembly processes will all have an impact, forming different spatial geometric structures, thereby obtaining MOF products with different structures and morphologies. As reported in research (Chemical Communications, 2018, 54, 252), using solvents with suitable polarity and solubility, with the assistance of coordination control reagents, and by controlling the nucleation and growth rate of crystals, five types of products with MOF materials with special morphology and size.

Under the appropriate synthesis conditions and protocols provided by the present invention, metal Mo and methylimidazole grow in one-dimensional directions after being combined, and the prepared Mo-MOF material is a uniform one-dimensional structured nanomaterial, instead of the usual MOF material. granular or blocky structure. If the Mo-MOF synthesis scheme of the present invention is changed, the Mo-MOF obtained will not be the one-dimensional structure of the invention. Furthermore, the synthesized one-dimensional Mo-MOF nanomaterial was subjected to selenization reaction. Using absolute ethanol as the solvent, the one-dimensional Mo-MOF nanomaterials were reacted with the hydrazine hydrate solution of selenium powder. The hydrazine hydrate solution of selenium powder can react with the Mo element in Mo-MOF to generate MoSe ₂ . MoSe ₂ has a two-dimensional lamellar structure. If the selenization reaction is too rapid, a large amount of MoSe ₂ will be generated in the reaction system. The MoSe ₂ lamellae will easily agglomerate and form a flower-like or spherical structure, which will reduce the catalytic activity of MoSe ₂ for the hydrogen evolution reaction. The number of lamellar edges weakens the catalytic performance of the material. The present invention uses absolute ethanol as a solvent, which can effectively slow down the selenization reaction rate of selenium powder hydrazine hydrate solution and one-dimensional Mo-MOF nanomaterials. Thus, the selenization reaction between the selenium source and Mo-MOF is controlled to only occur from the surface of Mo-MOF. Furthermore, at relatively high selenization reaction temperatures, Mo-MOF can still exist stably in absolute ethanol, and its one-dimensional structure will not be destroyed.

Under the suitable liquid phase system and synthesis conditions obtained through research in the present invention, only the surface of the one-dimensional Mo-MOF nanomaterial is selenized, the internal Mo-MOF still exists, and its one-dimensional nanostructure is still preserved, and the preparation A one-dimensional structure of MoSe ₂ /Mo-MOF composite nanomaterials was developed. The present invention creatively utilizes the composition and structural characteristics of Mo-MOF instead of only using Mo-MOF as a Mo source to participate in the selenization reaction. The reaction system of the present invention can effectively control the selenization reaction of one-dimensional Mo-MOF nanomaterials, and successfully prepares one-dimensional MoSe ₂ /Mo-MOF composite nanomaterials. If the synthesis scheme of the present invention is changed, the MoSe ₂ /Mo-MOF composite nanomaterial with one-dimensional structure cannot be obtained, and only a single MoSe ₂ material with a flower-like structure composed of agglomeration of conventional two-dimensional structure nanosheets is formed.

In the composite material prepared by the present invention, the presence of Mo-MOF is beneficial to the adsorption of water molecules by the material in an alkaline environment. MoSe ₂ nanosheets with catalytic activity for the hydrogen evolution reaction are grown on the one-dimensional Mo-MOF surface, allowing them to fully contact the solution, which is beneficial to the mass transfer process during the hydrogen evolution reaction. In addition, the growth of MoSe ₂ nanosheets on the one-dimensional Mo-MOF surface can avoid the agglomeration and accumulation of the sheets, allowing the active edges of the MoSe ₂ nanosheets to be fully exposed, thereby effectively increasing the material's active sites for the catalytic hydrogen evolution reaction. point. Therefore, the prepared one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial can show good catalytic performance for hydrogen evolution reaction in both acidic and alkaline environments.

Compared with the existing technology, the present invention prepares MoSe ₂ /Mo-MOF composite nanomaterials through a liquid phase method. The materials required for the preparation process are easy to obtain and low in cost. The experimental equipment and operation are simple, the reaction is controllable, and it is easy to repeat. As a hydrogen evolution reaction electrocatalyst, the MoSe ₂ /Mo-MOF composite nanomaterial prepared by the invention has excellent performance, low price, is applicable in both acidic and alkaline environments, and has good practical application value.

Description of the drawings

The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings;

Figure 1 is a scanning electron microscope image of the one-dimensional structure Mo-MOF nanomaterial obtained in Example 1;

Figure 2 is a scanning electron microscope image of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 1;

Figure 3 is the X-ray powder diffraction pattern spectrum of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 1;

Figure 4 is a thermogravimetric analysis curve diagram of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial and the one-dimensional structure Mo-MOF nanomaterial obtained in Example 1;

Figure 5 is a transmission electron microscope image of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 2;

Figure 6 is a scanning electron microscope image of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 3;

Figure 7 is a scanning electron microscope image of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 4;

Figure 8 is a scanning electron microscope image of the one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 5;

Figure 9 is a scanning electron microscope image of the bulk structure Mo-MOF obtained in Example 6;

Figure 10 is a scanning electron microscope image of the flower-like MoSe ₂ obtained in Example 7;

Figure 11 is a thermogravimetric analysis curve diagram of flower-like MoSe ₂ obtained in Example 7;

Figure 12 shows the polarity of the catalytic hydrogen evolution reaction of the one-dimensional MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 1 and the one-dimensional Mo-MOF nanomaterial, and the flower-like MoSe ₂ obtained in Example 7 in a 0.5 mol/LH ₂ SO ₄ solution. ization curve chart;

Figure 13 is a polarization curve diagram of the one-dimensional MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 1 and the one-dimensional Mo-MOF nanomaterial, and the flower-like MoSe ₂ obtained in Example 7 catalyzing the hydrogen evolution reaction in a 1 mol/L KOH solution. .

Detailed ways

Example 1

A method for preparing one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterials, including the following steps:

1) Weigh 0.4g of molybdenum trioxide (MoO ₃ ) powder and 0.332g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of deionized water in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the solution obtained in step 1) into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box at 110°C for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation and washed 5 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white one-dimensional Mo-MOF nanomaterials.

3) Weigh 0.2 mmol of selenium powder, add 2.5 mL of hydrazine hydrate (N ₂ H ₄ ·H ₂ O) solution with a mass fraction of 85%, and stir until the selenium powder is completely dissolved to obtain a selenium powder hydrazine hydrate solution. Add this solution dropwise to 30 mL of absolute ethanol, stir until the two solutions are evenly mixed, then add 0.03g of the one-dimensional Mo-MOF nanomaterial synthesized in step 2), and stir for 30 minutes to make the one-dimensional Mo- MOF nanomaterials are evenly dispersed in the solution.

4) Move the solution obtained in step 3) into a polytetrafluoroethylene-lined reactor with a volume of 50 mL, seal the reactor and place it in a constant temperature blast box, and heat the reaction at a constant temperature of 220°C for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation, washed 5 times with deionized water and absolute ethanol, and finally dried in a 60°C vacuum drying oven for 10 hours to obtain a one-dimensional structure MoSe ₂ /Mo-MOF. Composite nanomaterials.

Figure 1 is a scanning electron microscope image of the product Mo-MOF obtained in step 2) of Example 1. It shows that the product has a one-dimensional rod-like structure and a smooth surface. The diameter of the one-dimensional rod is about 500 nm to 900 nm and the length is about 10-20 microns. Figure 2 is a scanning electron microscope image of the product obtained in step 4) of Example 1. It can be seen that the product has a one-dimensional structure. But unlike the smooth surface of the one-dimensional rod-shaped Mo-MOF, the surface of this one-dimensional structure product is composed of nanosheets. The diameter of the one-dimensional structure product is about 500nm, and the thickness of the surface nanosheets is about 4 to 5nm. Figure 3 is the X-ray powder diffraction pattern spectrum of the product MoSe ₂ /Mo-MOF composite nanomaterial obtained in step 4) of Example 1. The position of its main diffraction peak is consistent with the standard card JCPDS No. 29- of hexagonal crystalline MoSe ₂ 0914 consistent. Figure 4 is a thermogravimetric analysis curve diagram of the product Mo-MOF material obtained in step 2) of Example 1 and the MoSe ₂ /Mo-MOF composite nanomaterial obtained in step 4). The thermogravimetric analysis curve shows that both the Mo-MOF material and the MoSe ₂ /Mo-MOF composite nanomaterial have a large weight loss stage between 300°C and 420°C, which corresponds to the high temperature of the ligands that constitute the Mo-MOF material. Decomposition temperature range. The X-ray powder diffraction pattern and thermogravimetric analysis curve show that after the selenization reaction, two-dimensional structured MoSe ₂ nanosheets are generated on the surface of the one-dimensional Mo-MOF material, and the internal Mo-MOF structure still exists. Example The product obtained in step 4) is a one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial.

Example 2

A method for preparing one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterials, including the following steps:

1) Weigh 0.5g of molybdenum trioxide (MoO ₃ ) powder and 0.432g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of deionized water in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the above solution into a polytetrafluoroethylene-lined reactor with a volume of 50 mL, seal the reactor and place it in a constant temperature blast box at 100°C for 14 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, the product in the kettle is collected by centrifugation, and washed 6 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white one-dimensional Mo-MOF nanomaterials.

3) Weigh 0.2 mmol of selenium powder, add 2.5 mL of hydrazine hydrate (N ₂ H ₄ ·H ₂ O) solution with a mass fraction of 85%, and stir until the selenium powder is completely dissolved to obtain a selenium powder hydrazine hydrate solution. Add this solution dropwise to 30 mL of absolute ethanol, stir until the two solutions are evenly mixed, then add 0.025g of the one-dimensional Mo-MOF nanomaterial synthesized in step 2), and stir for 30 minutes to make the one-dimensional Mo- MOF nanomaterials are evenly dispersed in the solution.

4) Move the solution in step 3) into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box. Heat the reaction at a constant temperature of 220°C for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation, washed 6 times with deionized water and absolute ethanol, and finally dried in a 60°C vacuum drying oven for 10 hours to obtain a one-dimensional structure of MoSe ₂ /Mo- MOF composite nanomaterials.

Figure 5 is a transmission electron microscope image of the product obtained in step 4) of Example 2. The image shows that the product is a one-dimensional nanostructure. The surface of the one-dimensional nanostructure is nanosheets and the interior is a solid structure. Transmission electron microscopy images show that during the selenization process of Mo-MOF with a one-dimensional nanorod structure, the surface of the nanorods undergoes a selenization reaction to generate two-dimensional structure MoSe ₂ nanosheets, and the interior remains as a solid Mo-MOF nanorod, forming a one-dimensional Structure of MoSe ₂ /Mo-MOF composite nanomaterials.

Example 3

A method for preparing one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterials, including the following steps:

1) Weigh 0.4g of molybdenum trioxide (MoO ₃ ) powder and 0.382g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of deionized water in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the above solution into a polytetrafluoroethylene-lined reactor with a volume of 50 mL, seal the reactor and place it in a constant temperature blast box at 110°C for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation and washed 5 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white one-dimensional Mo-MOF nanomaterials.

3) Weigh 0.2 mmol of selenium powder, add 2.5 mL of hydrazine hydrate (N ₂ H ₄ ·H ₂ O) solution with a mass fraction of 85%, and stir until the selenium powder is completely dissolved to obtain a selenium powder hydrazine hydrate solution. Add this solution dropwise to 30 mL of absolute ethanol, stir until the two solutions are evenly mixed, then add 0.02g of the one-dimensional Mo-MOF nanomaterial synthesized in step (2), and stir for 30 minutes to make the one-dimensional MoF -MOF nanomaterials are evenly dispersed in the solution.

4) Move the solution in step 3) into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box. Heat the reaction at a constant temperature of 200°C for 14 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation, washed 5 times with deionized water and absolute ethanol, and finally dried in a 60°C vacuum drying oven for 10 hours to obtain black one-dimensional MoSe ₂ /Mo- MOF composite nanomaterials.

Figure 6 is a scanning electron microscope image of the MoSe ₂ /Mo-MOF composite nanomaterial obtained in step 4) of Example 3. It can be seen that the material has a one-dimensional structure, and the surface of the one-dimensional structure material is composed of nanosheets.

Example 4

A method for preparing one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterials, including the following steps:

1) Weigh 0.3g of molybdenum trioxide (MoO ₃ ) powder and 0.252g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of deionized water in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the above solution into a polytetrafluoroethylene-lined reactor with a volume of 50 mL, seal the reactor and place it in a constant temperature blast box at 120°C for 10 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation and washed 5 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white one-dimensional Mo-MOF nanomaterials.

3) Weigh 0.2 mmol of selenium powder, add 2.5 mL of hydrazine hydrate (N ₂ H ₄ ·H ₂ O) solution with a mass fraction of 85%, and stir until the selenium powder is completely dissolved to obtain a selenium powder hydrazine hydrate solution. Add this solution dropwise to 30 mL of absolute ethanol, stir until the two solutions are evenly mixed, then add 0.03g of the one-dimensional Mo-MOF nanomaterial synthesized in step 2), and stir for 30 minutes to make the one-dimensional Mo- MOF nanomaterials are evenly dispersed in the solution.

4) Move the solution in step 3) into a polytetrafluoroethylene-lined reaction kettle with a volume of 50 mL. Seal the reaction kettle and place it in a constant temperature blast box. Heat the reaction at a constant temperature of 240°C for 10 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation, washed 6 times with deionized water and absolute ethanol, and finally dried in a 60°C vacuum drying oven for 10 hours to obtain black one-dimensional MoSe ₂ /Mo- MOF composite nanomaterials.

Figure 7 is a scanning electron microscope image of the MoSe ₂ /Mo-MOF composite nanomaterial obtained in step 4) of Example 4. It can be seen that the material has a one-dimensional structure, and the surface of the one-dimensional structure material is composed of nanosheets.

Example 5

A method for preparing one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterials, including the following steps:

1) Weigh 0.4g of molybdenum trioxide (MoO ₃ ) powder and 0.282g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of deionized water in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the above solution into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box at 100°C for 14 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation and washed 5 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white one-dimensional Mo-MOF nanomaterials.

3) Weigh 0.25 mmol of selenium powder, add 3 mL of hydrazine hydrate (N ₂ H ₄ ·H ₂ O) solution with a mass fraction of 85%, and stir until the selenium powder is completely dissolved to obtain a selenium powder hydrazine hydrate solution. Add this solution dropwise to 30 mL of absolute ethanol, stir until the two solutions are evenly mixed, and then add 0.03g of the one-dimensional Mo-MOF nanomaterial synthesized in step 2) to it. Stir for 30 minutes to evenly disperse the one-dimensional Mo-MOF nanomaterials in the solution.

4) Move the solution in step 3) into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box. Heat the reaction at a constant temperature of 200°C for 14 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation, washed several times with deionized water and absolute ethanol, and finally dried in a 60°C vacuum drying oven for 10 hours to obtain black one-dimensional MoSe ₂ /Mo- MOF composite nanomaterials.

Figure 8 is a scanning electron microscope image of the MoSe ₂ /Mo-MOF composite nanomaterial obtained in step 4) of Example 5. It can be seen that the material has a one-dimensional structure, and the surface of the one-dimensional structure material is composed of nanosheets.

Example 6 (for comparison)

A method for preparing bulk structure Mo-MOF, including the following steps:

1) Weigh 0.4g of molybdenum trioxide (MoO ₃ ) powder and 0.282g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of ethanol in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the above solution into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box at 100°C for 14 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation and washed 5 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white bulk Mo-MOF nanomaterials.

Figure 9 is a scanning electron microscope image of the Mo-MOF material obtained in step 2) of Example 6. It can be seen that the obtained Mo-MOF is a block-structured particle with a particle size ranging from 0.6 to 1.5 μm. This shows that the synthesis scheme of Example 6 cannot prepare one-dimensional structure Mo-MOF nanomaterials.

Example 7 (for comparison)

A preparation method of flower-like MoSe ₂ material, including the following steps:

1) Weigh 0.4g of molybdenum trioxide (MoO ₃ ) powder and 0.332g of imidazole (C ₃ H ₄ N ₂ ) and add them to 30 mL of deionized water in sequence, and stir until the two are completely dissolved to obtain a uniform white solution.

2) Move the above solution into a polytetrafluoroethylene-lined reactor with a volume of 50 mL, seal the reactor and place it in a constant temperature blast box at 110°C for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation and washed 5 times with deionized water and absolute ethanol. The product was dried at 60°C for 6 hours in a vacuum drying oven to obtain white one-dimensional Mo-MOF nanomaterials.

3) Weigh 0.2 mmol of selenium powder, add 2.5 mL of hydrazine hydrate (N ₂ H ₄ ·H ₂ O) solution with a mass fraction of 85%, and stir until the selenium powder is completely dissolved to obtain a selenium powder hydrazine hydrate solution. Add this solution dropwise to 30 mL of deionized water, stir until the two solutions are evenly mixed, and then add 0.03g of the one-dimensional Mo-MOF nanomaterial synthesized in step 2) into it. Stir for 30 minutes to evenly disperse the one-dimensional Mo-MOF nanomaterials in the solution.

4) Move the solution in step 3) into a polytetrafluoroethylene-lined reactor with a volume of 50 mL. Seal the reactor and place it in a constant temperature blast box. Heat the reaction at a constant temperature of 220°C for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product in the kettle is collected by centrifugation, washed 6 times with deionized water and absolute ethanol, and finally dried in a 60°C vacuum drying oven for 10 hours to obtain a flower-like structure MoSe ₂ material.

Figure 10 is a scanning electron microscope image of the MoSe ₂ material obtained in step 4) of Example 7. It can be seen that the material has a flower-like structure composed of a large number of nanosheets agglomerated, which shows that using the selenization scheme of Example 7, the original Mo-MOF The one-dimensional structure cannot be preserved. Figure 11 is a thermogravimetric analysis curve of the MoSe ₂ nanomaterial obtained in step 4) of Example 7. The thermogravimetric analysis curve shows that the material does not experience a large weight loss stage between 300°C and 420°C. This temperature range corresponds to the temperature range where the ligands constituting the Mo-MOF material decompose at high temperatures. This indicates that the use of Example 7 With the selenization scheme, what is obtained is not a MoSe ₂ /Mo-MOF composite material, but a single flower-like structure MoSe ₂ material.

Example 8

The application of a one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial in the field of catalytic electrolysis of water for hydrogen production. The specific application method is:

The one-dimensional structure MoSe ₂ /Mo-MOF composite nanomaterial obtained in Example 1 was used as a catalyst to test its performance in catalyzing the electrolysis of water for hydrogen evolution in acidic and alkaline environments. The catalytic electrolysis water hydrogen evolution reaction performance test is to use 0.5MH ₂ SO ₄ solution and 1M KOH solution at room temperature as the electrolyte solution in the acidic and alkaline environments for testing, and use a standard three-electrode system for testing. Graphite rods were used as counter electrodes, and silver/silver chloride (Ag/AgCl) electrodes were used as reference electrodes. The one-dimensional MoSe ₂ /Mo-MOF composite nanomaterials and one-dimensional Mo-MOF nanomaterials obtained in Example 1 were separated using Nafion reagent. , and the flower-like MoSe ₂ obtained in Example 7 was fixed on the surface of the glassy carbon electrode and used as a working electrode to conduct a catalytic hydrogen evolution reaction performance test using linear scanning voltammetry.

Figure 12 is a polarization curve diagram of the catalytic hydrogen evolution reaction of one-dimensional MoSe ₂ /Mo-MOF composite nanomaterials, one-dimensional Mo-MOF nanomaterials, and flower-like MoSe ₂ in 0.5 mol/LH ₂ SO ₄ solution. The test results show that in an acidic environment, compared with one-dimensional Mo-MOF nanomaterials, one-dimensional MoSe ₂ /Mo-MOF composite nanomaterials show obvious catalytic hydrogen evolution reaction performance, and compared with flower-like MoSe ₂ , its The catalytic hydrogen evolution reaction performance has been further improved.

Figure 13 is a polarization curve diagram of the catalytic hydrogen evolution reaction of one-dimensional MoSe ₂ /Mo-MOF composite nanomaterials, one-dimensional Mo-MOF nanomaterials, and flower-like MoSe ₂ in 1 mol/L KOH solution. Test results show that in an alkaline environment, compared with one-dimensional Mo-MOF nanomaterials and flower-like MoSe ₂ nanomaterials, one-dimensional MoSe ₂ /Mo-MOF composite nanomaterials have better catalytic hydrogen evolution reaction performance.

Claims (8)

1. The preparation method of the molybdenum diselenide/molybdenum-MOF composite nanomaterial with a one-dimensional structure is characterized by comprising the following steps of:

A. uniformly mixing a molybdenum source and imidazole in water, and performing a heating reaction on the obtained solution to obtain a one-dimensional nano-structure Mo-MOF;

B. dissolving a selenium source in hydrazine hydrate, adding the obtained hydrazine hydrate solution of the selenium source into absolute ethyl alcohol, adding the product obtained in the step A, uniformly stirring, and heating for reaction to obtain a molybdenum diselenide/molybdenum-MOF composite nanomaterial with a one-dimensional structure;

the mass ratio of the molybdenum source to the imidazole in the step A is 1: 1-2: 1, a step of;

the heating reaction in the step A refers to: reacting for 10-14 hours at the temperature of 90-120 ℃;

the morphology of the one-dimensional molybdenum diselenide/molybdenum-MOF composite nano material is as follows: moSe with two-dimensional structure grows on the surface of Mo-MOF with one-dimensional nano structure ₂ Nanosheets, one-dimensional MoSe structure ₂ The diameter of the composite nano material of the Mo-MOF is 400-900 nm, the length is 10-20 microns, and the MoSe on the surface of the composite material ₂ The thickness of the nano-sheet is 4-5 nm.

2. The method of claim 1, wherein the molybdenum source in step a is selected from molybdenum trioxide.

3. The method of claim 1 or 2, wherein in step a, the molybdenum source and water are used in a ratio of 1:50 to 100g/ml.

4. The method according to claim 1, wherein the volume ratio of the selenium source hydrazine hydrate solution to the absolute ethanol in the step B is 1:10 to 1:14.

5. the method according to claim 1 or 4, wherein the ratio of the mass of the product obtained in step A to the volume of absolute ethanol in step B is 1:1-2g/L.

6. The method according to claim 1, wherein the heating reaction in step B means: reacting for 10-14 hours at 200-240 ℃.

7. A one-dimensional molybdenum diselenide/molybdenum-MOF composite nanomaterial prepared by the preparation method of any one of claims 1 to 6, characterized in that the one-dimensional molybdenum diselenide/molybdenum-MOF composite nanomaterial has the morphology of: moSe with two-dimensional structure grows on the surface of Mo-MOF with one-dimensional nano structure ₂ Nanosheets, one-dimensional MoSe structure ₂ The diameter of the composite nano material of the Mo-MOF is 400-900 nm, the length is 10-20 microns, and the MoSe on the surface of the composite material ₂ The thickness of the nano-sheet is 4-5 nm.

8. Use of a one-dimensional molybdenum diselenide/molybdenum-MOF composite nanomaterial according to claim 7 for electrolytic water hydrogen evolution reactions.