阅读说明：本技术 一种Co掺杂的硒化钼纳米片/Mo箔复合材料、制备方法及其应用 (Co-doped molybdenum selenide nanosheet/Mo foil composite material, preparation method and application thereof ) 是由 王伟智 汪少振 李慰 朱勇 李慧 于 2021-09-28 设计创作，主要内容包括：本发明提供了一种Co掺杂的硒化钼纳米片/Mo箔复合材料、制备方法及其应用,首先利用电沉积的方式在钼箔表面沉积一层Co(OH)-(2),随后煅烧形成氧化物,最后再通过液相硒化的方法在钼箔表面生成MoSe-(2)纳米片,同时钼箔表面原本沉积的Co元素掺杂进入MoSe-(2)纳米片中,得到Co掺杂的硒化钼纳米片/Mo箔复合材料。与现有技术相比,本发明提供的制备工艺简洁,所用的原料简单、价廉易得,制备成本低,且反应可控、产率高,易于实现大规模化生产。所得的Co掺杂的硒化钼纳米片/Mo箔复合材料因其材料组成和结构的特点,可直接作为电极在酸性和碱性环境中催化电解水析氢反应,对于实际制氢工业具有优良的应用性能。(The invention provides a Co-doped molybdenum selenide nanosheet/Mo foil composite material, a preparation method and application thereof 2 Then calcining to form oxide, and finally generating MoSe on the surface of the molybdenum foil by a liquid-phase selenization method 2 Nanosheets, and Co originally deposited on the surface of the molybdenum foil is doped into MoSe 2 And obtaining the Co-doped molybdenum selenide nanosheet/Mo foil composite material from the nanosheets. Compared with the prior art, the preparation process provided by the invention is simple, the used raw materials are simple, cheap and easily available, the preparation cost is low, the reaction is controllable, the yield is high, and large-scale production is easy to realize. The obtained Co-doped molybdenum selenide nanosheet/Mo foil composite material can be directly used as an electrode to catalyze, electrolyze and separate out hydrogen in acidic and alkaline environments due to the characteristics of material composition and structure, and has excellent application performance for the actual hydrogen production industry.)

1. A preparation method of a Co-doped molybdenum selenide nanosheet/Mo foil composite material is characterized by comprising the following steps:

A. dissolving cobalt salt in water as electrolyte, adopting a three-electrode system, taking a molybdenum foil as a working electrode, Ag/AgCl as a reference electrode and a platinum sheet as a counter electrode, and carrying out electrochemical deposition on the surface of the molybdenum foil;

B. calcining the electrodeposited molybdenum foil prepared in the step A;

C. and D, adding N, N-dimethylformamide into a hydrazine hydrate solution of a selenium source, stirring until the N, N-dimethylformamide is uniformly mixed, adding the calcined molybdenum foil prepared in the step B, and heating and reacting under a closed condition to obtain the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

2. The process according to claim 1, wherein the cobalt salt used in step A is a soluble cobalt salt with or without water of crystallization.

3. The method according to claim 1 or 2, wherein in the electrolyte in step A, Co is added²⁺The concentration of (A) is 0.01-0.02 mol/L.

4. The production method according to claim 1 or 2, wherein electrochemical deposition is performed on the surface of the molybdenum foil in the electrolyte by using a three-electrode system, and the deposition is performed at a constant potential of-1.5V for 1-5 min.

5. The method as claimed in claim 1 or 2, wherein in step B, the calcination is carried out by heating at 480 ℃ and 520 ℃ for 0.5-1.5h under air atmosphere.

6. The method according to claim 1, wherein the concentration of the selenium source in the hydrazine hydrate solution of the selenium source in the step C is 0.05 to 0.2 mol/L.

7. The method according to claim 1 or 6, wherein the volume ratio of N, N-dimethylformamide to the solution of selenium source hydrazine hydrate added in step C is 30-40: 1.

8. The method as claimed in claim 1, wherein the heating reaction condition in step C is constant temperature heating reaction at 230 ℃ for 10-14 h.

9. A Co-doped molybdenum selenide nanosheet/Mo foil composite prepared by the preparation method of any one of claims 1-8.

10. Use of a Co-doped molybdenum selenide nanosheet/Mo foil composite prepared by the preparation method of any one of claims 1 to 8 in catalyzing an electrolytic hydro-evolution hydrogen reaction.

Technical Field

The invention belongs to the field of preparation of micro-nano materials, and particularly relates to a Co-doped molybdenum selenide nanosheet/Mo foil composite material, a preparation method and application thereof, which are used for researching the performance of an electrocatalytic hydrogen evolution reaction.

Background

With the progress of modern society, not only environmental problems are gradually worsened but also global energy shortage situation is becoming more and more serious due to the massive use of fossil fuels and the non-regenerability of fossil fuels themselves. Therefore, it is critical to find clean renewable energy sources to replace conventional fossil fuels. Hydrogen gas has a series of advantages of high abundance value, high calorific value, wide source, low cost, various storage modes, no pollution to the environment and the like, so hydrogen can be regarded as one of clean energy sources with the most potential to replace fossil fuels. And the efficient hydrogen production technology is an important foundation for promoting the development and the practical application of hydrogen energy.

The current techniques for producing hydrogen include a variety of: biomass hydrogen production, fossil fuel hydrogen production, and water splitting hydrogen production. Wherein, the electrolytic water is decomposed to prepare hydrogen without pollution, and the yield and the purity of the product are higher. However, in the process of water electrolysis, a larger external voltage is needed to overcome the overpotential generated by the hydrogen evolution reaction of water electrolysis, so that the cost of hydrogen production is increased. Therefore, the development of the catalyst with high efficiency, stability and low cost for catalyzing the electrolytic water hydrogen evolution reaction and reducing the cathode overpotential has important practical significance for saving energy and improving efficiency and solving the problem of energy shortage for a long time,

the platinum group (platinum, ruthenium, iridium, etc.) catalysts have the best electrocatalytic hydrogen evolution reaction capability, but the scarcity makes them inevitably inapplicable to practical production. In recent years, research shows that transition metal chalcogenides such as molybdenum disulfide and molybdenum diselenide also have electrocatalytic hydrogen evolution performance, and therefore, the transition metal chalcogenides are widely researched and reported. The molybdenum disulfide and the molybdenum diselenide are two-dimensional layered compounds and have larger surface area and catalytic activity. The research now finds that the catalytic sites of molybdenum disulfide and molybdenum diselenide are positioned at the edge of the layered structure, and the basal surfaces of the molybdenum disulfide and molybdenum diselenide are mostly inert. The characteristics of the layered structure also make the molybdenum disulfide and molybdenum diselenide materials easy to accumulate and agglomerate, which is not beneficial to the exposure of the layered edge with catalytic activity. In addition, the conductivity of the molybdenum disulfide and molybdenum diselenide materials is not high, so that the electron transmission rate in the electrolytic water hydrogen evolution reaction process is limited. These limit the performance of electrocatalytic hydrogen evolution reactions of molybdenum disulfide and molybdenum diselenide materials.

The powdered hydrogen evolution reaction catalyst is usually fixed on the surface of an electrode by using a binder. The use of the binder can reduce the exposure of active sites of the catalyst and reduce the catalytic activity of the catalyst, and meanwhile, most of the binder is organic, so that the binder is not beneficial to electron transfer in the electrocatalysis process, and the resistance is increased.

Disclosure of Invention

The invention aims to provide a Co-doped molybdenum selenide nanosheet/Mo foil composite material and a preparation method thereof, raw materials, equipment and a process adopted in the preparation process are simple, convenient and low in production cost.

The invention also aims to provide application of the Co-doped molybdenum selenide nanosheet/Mo foil composite material in catalyzing and electrolyzing water, and the Co-doped molybdenum selenide nanosheet/Mo foil composite material has good reaction performance in catalyzing, electrolyzing, hydrolyzing and hydrogen evolution under acid and alkali environments.

The specific technical scheme of the invention is as follows:

a preparation method of a Co-doped molybdenum selenide nanosheet/Mo foil composite material comprises the following steps:

A. dissolving cobalt salt in water as electrolyte, adopting a three-electrode system, taking a molybdenum foil as a working electrode, Ag/AgCl as a reference electrode and a platinum sheet as a counter electrode, and carrying out electrochemical deposition on the surface of the molybdenum foil;

B. calcining the electrodeposited molybdenum foil prepared in the step A;

C. and D, adding N, N-dimethylformamide into a hydrazine hydrate solution of a selenium source, stirring until the N, N-dimethylformamide is uniformly mixed, adding the calcined molybdenum foil prepared in the step B, and heating and reacting under a closed condition to obtain the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

In step A, the cobalt salt used in step A is a soluble cobalt salt with or without crystal water, preferably cobalt chloride or cobalt nitrate with or without crystal water.

In the electrolyte described in step A, Co²⁺The concentration of (A) is 0.01-0.02 mol/L. The water is deionized water; the volume of the resulting electrolyte was 50 mL.

In the step A, electrochemical deposition is carried out on the surface of the molybdenum foil by adopting a three-electrode system in electrolyte, the deposition is carried out by using a constant potential with the potential of-1.5V (vs. Ag/AgCl), the deposition time is 1-5min, and Co (OH) is obtained by deposition on the surface of the molybdenum foil₂。

Step B, washing the surface of the electrodeposited molybdenum foil with deionized water before calcination;

in the step B, the calcination refers to the constant-temperature heating reaction at 480-520 ℃ for 0.5-1.5h in a muffle furnace under the air atmosphere. After the reaction is finished, the muffle furnace is naturally cooled to room temperature, the molybdenum foil is taken out, and Co (OH) is electrodeposited on the surface of the molybdenum foil₂Conversion to Co₃O₄。

The preparation method of the hydrazine hydrate solution of the selenium source in the step C comprises the following steps: adding a selenium source into hydrazine hydrate, and stirring until the selenium source is completely dissolved to obtain the selenium-enriched hydrazine hydrate.

The selenium source is selenium powder (Se) or selenium dioxide (SeO)₂) Any one of the above; the mass concentration of the hydrazine hydrate is more than or equal to 85 percent. The concentration of the selenium source in the hydrazine hydrate solution of the selenium source is 0.05-0.2 mol/L.

And D, adding the N, N-dimethylformamide and the selenium source hydrazine hydrate solution in the step C in a volume ratio of 30-40: 1.

In the step C, the heating reaction condition is constant temperature heating reaction at the temperature of 190-230 ℃ for 10-14 h.

And C, after the reaction in the step C is finished, naturally cooling the reaction kettle to room temperature, taking out, cleaning and drying to obtain a product, namely the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

The invention provides a Co-doped molybdenum selenide nanosheet/Mo foil composite material, which is prepared by the method and comprises the following steps: doping MoSe on the surface of molybdenum foil₂Nanosheets. MoSe₂The thickness of the nanosheet is 2-3 nm, the size of the nanosheet is 100-150 nm, and the doping amount of Co is 3-7 atomic percent.

The invention provides an application of a Co-doped molybdenum selenide nanosheet/Mo foil composite material, which specifically comprises the following steps: the application in catalyzing electrolysis water hydrogen evolution reaction. The prepared Co-doped molybdenum selenide nanosheet/Mo foil composite material can be directly used as an electrode material to be applied to catalytic electrolysis water hydrogen evolution reaction in an acidic or alkaline environment, and has good catalytic electrolysis water hydrogen evolution reaction performance in different pH environments.

The invention firstly deposits a layer of Co (OH) on the surface of the molybdenum foil substrate by an electrodeposition method₂Further converted into Co by calcination₃O₄. In the subsequent reaction, the molybdenum foil reacts in hydrazine hydrate solution of N, N-dimethylformamide and selenium source to generate MoSe on the surface of the molybdenum foil in situ₂Nanosheets, Co attached to the surface of the molybdenum foil by electrodeposition and calcination simultaneously₃O₄Co element in the molybdenum foil is doped into MoSe grown in situ on the molybdenum foil₂And finally obtaining the Co-doped molybdenum selenide nanosheet/Mo foil composite material in the nanosheet structure.

When the powder hydrogen evolution reaction catalyst is used, a binder is needed to fix the powder hydrogen evolution reaction catalyst on the surface of an electrode, which can hinder the exposure of active sites of the catalyst, reduce the electron transmission rate in the reaction process, increase the reaction resistance and weaken the catalytic performance of the catalyst. The self-supporting electrode of the catalyst material directly grows on the conductive substrate, does not need to use a binder, and can be directly used as an electrode for catalyzing the electrolytic water hydrogen evolution reaction, thereby avoiding the increase of resistance and improving the transmission rate of electrons. Meanwhile, the self-supporting electrode can avoid the accumulation phenomenon of the powdery catalyst, can effectively ensure the number of active sites, and enables the catalyst to be in close contact with electrolyte, thereby improving the catalytic hydrogen evolution reaction performance of the electrode. The Co-doped molybdenum selenide nanosheets prepared by the method directly grow on a molybdenum foil substrate with excellent conductivity, can be directly used as a self-supporting electrode for catalyzing electrolysis water hydrogen evolution reaction, do not need to use a binder, avoid the increase of resistance, and can enhance the transmission rate of electrons. Meanwhile, the Co-doped molybdenum selenide nanosheets grow on the surface of the molybdenum foil, so that the nanosheets are prevented from being stacked, the catalytic active sites of the hydrogen evolution reaction positioned at the edge of the molybdenum selenide layer can be fully exposed, the catalyst is in close contact with the electrolyte, and the charge in the process of catalyzing the hydrogen evolution reaction is facilitatedAnd mass transfer. Co doping energy activated MoSe₂The electric catalytic activity of the Se site on the base surface of the nano sheet, and the Co site can also become a new active site, so that the number of the catalytic active sites of the prepared material is further increased, and the catalytic performance of the material is improved.

According to the invention, the molybdenum foil is used as the substrate of the self-supporting electrode, the molybdenum foil has excellent conductivity, and the Co-doped molybdenum selenide nanosheets grow on the surface of the molybdenum foil, so that the electronic transfer between the catalytic active sites and the electrode is facilitated. And the molybdenum foil is good in acid resistance and alkali resistance. The material can be applied to acid-base environments, and is more favorable for meeting the practical application requirements of the hydrogen production process by water electrolysis. In addition, in the material preparation process, the molybdenum foil is used as a substrate and a reactant, so that the cost of the material preparation process is reduced.

The invention firstly utilizes the mode of electrodeposition to deposit a layer of Co (OH) on the surface of the molybdenum foil₂Then calcining to form oxide, and finally generating MoSe on the surface of the molybdenum foil by a liquid-phase selenization method₂Nanosheets, and Co originally deposited on the surface of the molybdenum foil is doped into MoSe₂And obtaining the Co-doped molybdenum selenide nanosheet/Mo foil composite material from the nanosheets.

The selenium source is dissolved in the hydrazine hydrate, which is beneficial to the uniform dispersion of the selenium source in the reaction system. In the subsequent reaction process, hydrazine hydrate can further reduce selenium source under heating condition to generate hydrogen selenide (H)₂Se). The formed hydrogen selenide further reacts with the molybdenum foil to generate MoSe₂。

Reaction of molybdenum foil with hydrogen selenide to form MoSe₂In the process, Co element on the surface of the molybdenum foil is doped into the generated MoSe₂And obtaining the Co-doped molybdenum selenide nanosheets from the nanosheets. Because Co element is attached to the surface of the molybdenum foil in the form of a small amount of oxide after electrodeposition and calcination, the Co element can be effectively doped into the surface of the molybdenum foil to react with hydrogen selenide to generate MoSe₂And obtaining the Co-doped molybdenum selenide nanosheet/Mo foil composite material from the nanosheets. If Co element is attached to the surface of the molybdenum foil in the form of oxide without adopting electrodeposition and calcination, the pure molybdenum foil is reacted with hydrazine hydrate of selenium source, and in the system of the reaction of the pure molybdenum foil and the hydrazine hydrateSoluble cobalt salt is directly added to provide Co element, so that free Co ions in the solution can easily react with hydrogen selenide directly to form cobalt selenide precipitate. After the pure molybdenum foil reacts with hydrazine hydrate of a selenium source, single MoSe is formed on the surface of the molybdenum foil₂It is difficult to obtain Co-doped molybdenum selenide nanosheets.

In the reaction process, N-dimethylformamide is adopted as a liquid phase reaction system. Because the N, N-dimethylformamide is alkalescent, the reaction rate of hydrogen selenide generated by the reaction of hydrazine hydrate and selenium source and the molybdenum foil can be slowed down, and uniform MoSe can be generated on the surface of the molybdenum foil₂Nanosheets. Meanwhile, the alkalescent reaction environment is favorable for stable attachment of Co oxide on the surface of the molybdenum foil, so that Co element is doped with generated MoSe in the reaction process of hydrogen selenide and the molybdenum foil₂Finally, obtaining the Co-doped molybdenum selenide nanosheet on the surface of the molybdenum foil. If ethanol or a mixed solution of ethanol and water is used as a liquid-phase reaction system, Co oxide on the surface of the molybdenum foil is easy to fall off in the reaction process, and Co-doped molybdenum selenide nanosheets cannot be obtained on the surface of the molybdenum foil. If pure water is used as a liquid phase reaction system, the reaction rate of hydrogen selenide generated by the reaction of hydrazine hydrate and a selenium source and molybdenum foil cannot be slowed down. Hydrogen selenide reacts with molybdenum foil at too fast a rate, resulting in the formation of MoSe₂Peeling off from the surface of the molybdenum foil, and uniform MoSe can not be generated on the surface of the molybdenum foil₂Nanosheets. Thus, Co-doped molybdenum selenide nanosheet/Mo foil composite material cannot be prepared

Compared with the prior art, the preparation process of the Co-doped molybdenum selenide nanosheet/Mo foil composite material provided by the invention is simple, the used raw materials are simple, cheap and easily available, the preparation cost is low, the reaction is controllable, the yield is high, and the large-scale production is easy to realize. The obtained Co-doped molybdenum selenide nanosheet/Mo foil composite material can be directly used as an electrode to catalyze, electrolyze and separate out hydrogen in acidic and alkaline environments due to the characteristics of material composition and structure, and has excellent application performance for the actual hydrogen production industry.

Drawings

The following further describes embodiments of the present invention with reference to the drawings.

FIG. 1 is a scanning electron microscope image of the Co-doped molybdenum selenide nanosheet/Mo foil composite obtained in example 1;

FIG. 2 is an X-ray diffraction pattern of a sample obtained from the Co-doped molybdenum selenide nanosheet/Mo foil composite material obtained in example 1 after being peeled from the surface of a molybdenum foil by ultrasound;

FIG. 3 is an X-ray photoelectron spectrum of a sample peeled from the surface of a molybdenum foil by ultrasound of the Co-doped molybdenum selenide nanosheet/Mo foil composite material obtained in example 1;

FIG. 4 is an X-ray energy spectrum of a sample obtained by peeling the Co-doped molybdenum selenide nanosheet/Mo foil composite material obtained in example 2 from the surface of a molybdenum foil by ultrasound;

FIG. 5 is a scanning electron microscope image of the Co-doped molybdenum selenide nanosheet/Mo foil composite obtained in example 2;

FIG. 6 is a scanning electron microscope image of the Co-doped molybdenum selenide nanosheet/Mo foil composite obtained in example 3;

FIG. 7 is a transmission electron micrograph of a sample of the Co-doped molybdenum selenide nanosheet/Mo foil composite obtained in example 4 peeled from the surface of the molybdenum foil by ultrasound;

FIG. 8 shows the Co-doped molybdenum selenide nanosheet/Mo foil composite, Mo foil, MoSe obtained in example 1₂Mo foil in H₂SO₄A polarization curve diagram of the catalytic hydrogen evolution reaction in the solution;

FIG. 9 shows the Co-doped molybdenum selenide nanosheet/Mo foil composite, Mo foil, MoSe obtained in example 1₂Polarization diagram of the catalyzed hydrogen evolution reaction of a/Mo foil in KOH solution.

Detailed description of the preferred embodiments

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified. The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.

Example 1

A preparation method of a Co-doped molybdenum selenide nanosheet/Mo foil composite material comprises the following steps:

A. weigh 0.5mmol of CoCl₂·6H₂O is added to 50mL of deionized water and stirred until completely dissolved. The solution was used as an electrolyte, a three-electrode system was used, a 4cm x l cm molybdenum foil was used as a working electrode, a platinum sheet was used as a counter electrode, and Ag/AgCl was used as a reference electrode, and electrochemical deposition was carried out for 3min at a constant potential of-1.5V (vs Ag/AgCl).

B. After the electrodeposition is finished, the molybdenum foil is washed by deionized water and then is placed in a muffle furnace to be calcined for 1h at 500 ℃ in the air atmosphere.

C. 0.05mmol of selenium powder is weighed and added into 1mL of hydrazine hydrate (mass concentration is 85 percent), and the mixture is stirred until the selenium powder is completely dissolved. Then, 30mL of N, N-dimethylformamide was added thereto, and the mixture was stirred until uniform. The mixed solution was transferred to a teflon inner liner of a 50mL high-pressure reactor, and then the calcined molybdenum foil with Co deposited was placed therein, and the reactor was closed and then placed in a constant temperature forced air drying oven to react at 220 ℃ for 12 hours. And after the reaction is finished, taking out the molybdenum foil after the reaction kettle is naturally cooled to room temperature. And sequentially washing the composite material by deionized water and absolute ethyl alcohol for 5 times, and then drying the cleaned composite material in a vacuum drying oven at 60 ℃ for 6 hours to obtain the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

FIG. 1 is a scanning electron microscope image of the product obtained in example 1, which shows that the product is a nanosheet material formed on the surface of a molybdenum foil, and the thickness of the lamella is about 2-3 nm.

FIG. 2 is an X-ray diffraction pattern of a sample obtained by ultrasonically peeling the product obtained in example 1 from the surface of a molybdenum foil, in which main diffraction peaks and MoSe are shown₂The powder diffraction standard card JCPDS 29-0914 is matched, and the sheet layer on the surface of the molybdenum foil is mainly MoSe₂。

FIG. 3 is an X-ray photoelectron spectrum of a sample obtained by ultrasonically peeling the surface of a molybdenum foil from the product obtained in example 1, and shows that the product is mainly composed of two elements of Se and Mo, and contains a small amount of Co element, the content of the Co element is only about 5% (atomic percent), which indicates that the product formed on the surface of the molybdenum foil is Co-doped MoSe₂A material.

Example 2

A preparation method of a Co-doped molybdenum selenide nanosheet/Mo foil composite material comprises the following steps:

A. weigh 0.5mmol of CoCl₂·6H₂O is added to 50mL of deionized water and stirred until completely dissolved. The solution was used as an electrolyte, a three-electrode system was used, a 4cm x l cm molybdenum foil was used as a working electrode, a platinum sheet was used as a counter electrode, and Ag/AgCl was used as a reference electrode, and electrochemical deposition was carried out for 5min at a constant potential of-1.5V (vs Ag/AgCl).

B. After the electrodeposition is finished, the molybdenum foil is washed by deionized water and then is placed in a muffle furnace to be calcined for 1h at 500 ℃ in the air atmosphere.

C. 0.05mmol of selenium powder is weighed and added into 1mL of hydrazine hydrate (mass concentration is 85 percent), and the mixture is stirred until the selenium powder is completely dissolved. Then, 30mL of N, N-dimethylformamide was added thereto, and the mixture was stirred until uniform. The mixed solution was transferred to a teflon inner liner of a 50mL high-pressure reactor, and then the calcined molybdenum foil with Co deposited was placed therein, and the reactor was closed and then placed in a constant temperature forced air drying oven to react at 220 ℃ for 12 hours. And after the reaction is finished, taking out the molybdenum foil after the reaction kettle is naturally cooled to room temperature. And sequentially washing with deionized water and absolute ethyl alcohol for several times, and drying in a vacuum drying oven at 60 ℃ for 6 hours to obtain the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

FIG. 4 is an X-ray energy spectrum of a sample obtained by ultrasonically peeling the product of example 2 from the surface of a molybdenum foil, and shows that the product is mainly composed of two elements of Se and Mo, and contains a small amount of Co element, and the content of the Co element is only about 7% (atomic percent), indicating that the product formed on the surface of the molybdenum foil is Co-doped MoSe₂A material.

FIG. 5 shows the product obtained in example 2Scanning electron micrograph of the material shows that the product is Co-doped MoSe formed on the surface of the molybdenum foil₂The nanosheet is made of nanosheets, and the thickness of the nanosheets is about 2-3 nm.

Example 3

A preparation method of a Co-doped molybdenum selenide nanosheet/Mo foil composite material comprises the following steps:

A. weigh 1mmol of Co (NO)₃)₂Added to 50mL of deionized water and stirred until completely dissolved. The solution was used as an electrolyte, a three-electrode system was used, a 4cm x l cm molybdenum foil was used as a working electrode, a platinum sheet was used as a counter electrode, and Ag/AgCl was used as a reference electrode, and electrochemical deposition was carried out for 1min at a constant potential of-1.5V (vs Ag/AgCl).

B. After the electrodeposition is finished, the molybdenum foil is washed by deionized water and then is placed in a muffle furnace to be calcined for 0.5h at 520 ℃ in an air atmosphere.

C. 0.2mmol of selenium powder is weighed and added into 1mL of hydrazine hydrate (mass concentration is 85 percent), and the mixture is stirred until the selenium powder is completely dissolved. Then, 40mL of N, N-dimethylformamide was added thereto, and the mixture was stirred until uniform. The mixed solution was transferred to a teflon inner liner of a 50mL high-pressure reactor, and then the calcined molybdenum foil with Co deposited was placed therein, and the reactor was closed and then placed in a constant temperature forced air drying oven to react at 230 ℃ for 10 hours. And after the reaction is finished, taking out the molybdenum foil after the reaction kettle is naturally cooled to room temperature. And sequentially washing with deionized water and absolute ethyl alcohol for several times, and drying in a vacuum drying oven at 60 ℃ for 6 hours to obtain the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

FIG. 6 is a scanning electron micrograph of the product obtained in example 3, showing that the product is Co-doped MoSe formed on the surface of the molybdenum foil₂The nanosheet is made of nanosheets, and the thickness of the nanosheets is about 2-3 nm.

Example 4

A preparation method of a Co-doped molybdenum selenide nanosheet/Mo foil composite material comprises the following steps:

A. weigh 1mmol of CoCl₂·6H₂O is added to 50mL of deionized water and stirred until completely dissolved. The solution is used as electrolyte, and a three-electrode system is adopted, wherein the thickness of the three-electrode system is 4cm multiplied by l cmThe molybdenum foil is used as a working electrode, the platinum sheet is used as a counter electrode, Ag/AgCl is used as a reference electrode, and electrochemical deposition is carried out for 5min under the constant potential of-1.5V (relative to Ag/AgCl).

B. After the electrodeposition is finished, the molybdenum foil is washed by deionized water and then is placed in a muffle furnace to be calcined for 1.5h at 480 ℃ in the air atmosphere.

C. 0.05mmol of selenium dioxide is weighed into 1mL of hydrazine hydrate (85 mass concentration), and stirred until the selenium dioxide is completely dissolved. Then, 40mL of N, N-dimethylformamide was added thereto, and the mixture was stirred until uniform. The mixed solution was transferred to a teflon inner liner of a 50mL high-pressure reactor, and then the calcined molybdenum foil with Co deposited was placed therein, and the reactor was closed and then placed in a constant temperature forced air drying oven to react at 190 ℃ for 14 hours. And after the reaction is finished, taking out the molybdenum foil after the reaction kettle is naturally cooled to room temperature. And sequentially washing with deionized water and absolute ethyl alcohol for several times, and drying in a vacuum drying oven at 60 ℃ for 6 hours to obtain the Co-doped molybdenum selenide nanosheet/Mo foil composite material.

FIG. 7 is a transmission electron micrograph of a sample of the product obtained in example 4 ultrasonically peeled from the surface of a molybdenum foil, showing Co-doped MoSe formed on the surface of the molybdenum foil₂The nano-sheet is of a lamellar nano-structure, and the size of the nano-sheet is about 100-150 nm.

Example 5

The application of the Co-doped molybdenum selenide nanosheet/Mo foil composite material directly serving as an electrode in the field of hydrogen production by catalytic electrolysis of water is as follows:

the Co-doped molybdenum selenide nanosheet/Mo foil composite material obtained in the example 1 is directly applied as an electrode for testing the performance of the catalytic electrolysis water hydrogen evolution reaction in acidic and alkaline environments. The performance test of the catalytic electrolysis water hydrogen evolution reaction is carried out at room temperature by adopting a standard three-electrode system. The Co-doped molybdenum selenide nanosheet/Mo foil composite material is directly used as a working electrode, a graphite rod is used as a counter electrode, a silver/silver chloride (Ag/AgCl) electrode is used as a reference electrode, the catalytic hydrogen evolution reaction performance of the material is tested by linear scanning voltammetry at a sweep rate of 5mV/s, and 0.5M H is respectively used₂SO₄The solution, 1M KOH solution, is used as the electrolyte solution under the acidic and alkaline environment for testing. For comparison, Mo foil, MoSe, on which no material was grown on the surface, were also tested in the same acid and alkaline environments using the same test method₂The catalytic hydrogen evolution reaction performance of the/Mo foil material. MoSe₂The MoSe was synthesized from the material of the Journal of Materials Chemistry A2014, 2, 360 of the reference Mo foil₂Nano material to synthesize MoSe₂Ultrasonically dispersing the nano material in an ethanol solution of Nafion, dropwise adding the uniformly dispersed liquid on the surface of a Mo foil, standing at room temperature and drying to obtain MoSe for testing₂a/Mo foil material.

FIG. 8 shows the Co-doped molybdenum selenide nanosheet/Mo foil composite obtained in example 1, Mo foil without any material grown on the surface thereof, and MoSe₂The content of the Mo foil is 0.5mol/L H₂SO₄Polarization curve of catalytic hydrogen evolution reaction in solution. The test result shows that the Mo foil and the MoSe which have no material grown on the surface₂Compared with the Mo foil, the Co-doped molybdenum selenide nanosheet/Mo foil composite material has better catalytic hydrogen evolution performance in an acidic environment. Showing a single MoSe phase₂Co doping increases MoSe₂The catalytic activity site number of the catalyst is increased, thereby improving the catalytic hydrogen evolution reaction performance of the material.

FIG. 9 shows the Co-doped molybdenum selenide nanosheet/Mo foil composite material obtained in example 1 and Mo foil and MoSe having no material grown on the surface thereof₂Polarization curve of the catalytic hydrogen evolution reaction of the/Mo foil in 1mol/L KOH solution. The test result shows that the Mo foil and the MoSe which have no material grown on the surface₂Compared with the Mo foil, the Co-doped molybdenum selenide nanosheet/Mo foil composite material has better catalytic hydrogen evolution performance in an alkaline environment. Showing a single MoSe phase₂Co doping increases MoSe₂The catalytic activity site number of the catalyst is increased, thereby improving the catalytic hydrogen evolution reaction performance of the material.

The product of the present invention cannot be obtained by using ethanol, water, or a mixed solution of ethanol and water as a reaction solution. But the failed product was not tested for catalytic performance.