Preparation method and application of transition metal selenide / metallic molybdenum disulfide in-plane heterostructure

Abstract

The application belongs to the technical field of materials, and provides a preparation method of transition metal selenide / metallic phase molybdenum disulfide in-plane heterostructure and application thereof. The method is to take metallic phase molybdenum disulfide nanosheet as a main body, embed 2-5 nm transition metal selenide nanoclusters into the interior of the metallic phase molybdenum disulfide nanosheet, and make the two be in the same plane. The specific steps are as follows: a transition metal sulfide in-plane heterostructure prepared by a two-step hydrothermal method is used as a precursor, a gas phase selenization method is used to convert the in-plane transition metal sulfide into its selenide under the premise of retaining the metallic phase molybdenum disulfide, and a transition metal selenide / metallic phase molybdenum disulfide in-plane heterostructure is obtained. The prepared transition metal selenide / metallic phase molybdenum disulfide in-plane heterostructure powder and self-supporting electrode are used as a water electrolysis hydrogen evolution catalyst. The preparation process is simple, the price is low, and the method is green and environment-friendly. The material has super-high catalytic activity as the water electrolysis hydrogen evolution catalyst.

Description

Technical Field

[0001] This invention belongs to the field of materials, and particularly relates to a method for preparing a transition metal selenide / metallic phase molybdenum disulfide in-plane heterostructure and its application. Background Technology

[0002] Currently, the electrochemical hydrogen evolution reaction (HER) is considered a key technology for green energy storage and utilization, but its scalability is limited by the reserves and cost of noble metal-based catalysts. Molybdenum disulfide (MoS2), as a cost-effective and highly efficient electrocatalytic HER catalyst, shows great promise. Theoretical and experimental studies have shown that a few active sites in MoS2 are located at the edges and defects, while the basal plane containing a large number of active sites exhibits catalytic inertness, severely limiting its overall catalytic activity. In nature, molybdenum disulfide exists mainly in three forms: 1T-MoS2, 2H-MoS2, and 3R-MoS2. Among these three, metallic molybdenum disulfide (1T-MoS2) exhibits superior electrocatalytic HER activity compared to semiconductor molybdenum disulfide (2H-MoS2) due to its excellent metallic conductivity, which significantly reduces its charge transfer resistance.

[0003] Studies have shown that heterostructures enhance catalytic activity by activating the basal surface of molybdenum disulfide through various effects, including generating new catalytic sites, increasing conductivity, and improving reaction kinetics. According to existing reports, most reported 1T-MoS2-based heterostructures are out-of-plane heterostructures, meaning that 1T-MoS2 nanosheets are bonded to a second phase via chemical bonds or weak binding forces such as out-of-plane van der Waals interactions. This can result in a second phase deposited on the 1T-MoS2 nanosheet basal surface, or conversely, 1T-MoS2 nanosheets being laterally deposited on the second phase. Such out-of-plane heterostructures not only easily lead to the masking of the heterointerface but also to the masking of the active sites on the 1T-MoS2 basal surface, preventing sufficient contact with the electrolyte and thus limiting their hydrogen evolution catalytic activity.

[0004] Molybdenum disulfide readily undergoes phase transformation at high temperatures, resulting in a change from a metallic phase to a semiconductor phase. Transition metal selenides are often prepared using high-temperature vapor-phase selenization methods, which makes heterostructures of metallic molybdenum disulfide-based transition metal selenides rarely reported.

[0005] Currently, the construction of out-of-plane heterostructures based on molybdenum disulfide in the metal phase is limited by the limited regulation and activation of sulfur atoms on the basal plane, which severely restricts their electrocatalytic hydrogen evolution activity. At the same time, the insufficient stability of molybdenum disulfide in the metal phase at high temperatures also limits the construction of heterostructures with transition metal selenides. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a transition metal selenide / metallic phase molybdenum disulfide in-plane heterostructure and its application, aiming to solve the problems mentioned in the background art.

[0007] This invention is achieved as follows: a transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. This structure uses basic carbonate as a structural template and metal phase molybdenum disulfide nanosheets as the main body. Transition metal selenide nanoclusters are uniformly embedded in the metal phase molybdenum disulfide nanosheets, and are in the same plane as the metal phase molybdenum disulfide, with a size of 2-5 nm. The content of metal phase molybdenum disulfide in the molybdenum disulfide is 60-75%. The metal phase molybdenum disulfide in this structure has thermal stability.

[0008] A further technical solution involves transition metal selenides, including but not limited to cobalt selenide, nickel selenide, iron selenide, and zinc selenide. The thermal stability of molybdenum disulfide refers to the fact that the molybdenum disulfide in the precursor transition metal sulfide / molybdenum disulfide in-plane heterostructure does not transform into the semiconductor phase molybdenum disulfide after a high-temperature gas-phase selenization reaction at 350°C. This transition metal selenide / molybdenum disulfide in-plane heterostructure can effectively enhance the basal activity of the molybdenum disulfide basal surface, thereby reducing the overpotential of the electrocatalytic hydrogen evolution reaction and ultimately achieving efficient water electrolysis for hydrogen production.

[0009] Another object of the present invention is to provide a method for preparing a transition metal selenide / metallic phase molybdenum disulfide in-plane heterostructure, comprising the following steps:

[0010] Step 1: Preparation of transition metal basic carbonate precursors. Specifically, the transition metal salt and an appropriate amount of nucleating agent are dissolved in a mixed solution of water and ethanol, and the solution is placed in a sealed reaction vessel to prepare basic carbonates via a hydrothermal method. The hydrothermal reaction temperature is 90-140℃, and the reaction time is 5-12 hours.

[0011] Step 2: Prepare the in-plane heterostructure of transition metal sulfide molybdenum disulfide. Specifically, take the transition metal basic carbonate prepared in Step 1, weigh out molybdenum trioxide (as molybdenum source), sulfur source, and appropriate amount of reducing agent according to the ratio, add appropriate amount of water and mix evenly. Place the mixture in a sealed reaction vessel for hydrothermal reaction at a reaction temperature of 180-240℃ for 8-24h.

[0012] Step 3: Prepare a transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, place the transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure obtained in Step 2 under a selenium vapor atmosphere for a gas-phase selenization reaction. The reaction temperature of the gas-phase selenization reaction is 300-400℃, and the reaction time is 1-3h.

[0013] Step 4: The transition metal selenide / metal phase molybdenum disulfide powder obtained from the gas-phase selenization reaction in Step 3 is washed with carbon disulfide, ethanol and deionized water respectively and then dried to obtain the product, transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure.

[0014] In a further technical solution, in step one, the transition metal salts mainly include cobalt nitrate, ferric nitrate, nickel nitrate, and zinc nitrate, and the nucleating agents include urea and ammonium fluoride.

[0015] The sulfur source in step two is selected from one or more of thioacetamide or sodium sulfide, and the reducing agent is selected from any one or more of urea or hydrazine hydrate.

[0016] In step one, the ratio of water to ethanol is 1:1;

[0017] The ratio of the number of molybdenum atoms in the molybdenum trioxide in step two to the number of sulfur atoms in the sulfur source is 1:5-40.

[0018] In a further technical solution, in step three, the selenium vapor atmosphere is formed by the high-temperature decomposition of selenium powder in an inert atmosphere, which includes pure nitrogen and argon. The atmosphere should be higher than atmospheric pressure during the reaction.

[0019] The mass ratio of the selenium powder to the transition metal sulfide metal phase molybdenum disulfide in-plane heterostructure powder is 40-100:1.

[0020] In a further technical solution, in step three, the temperature of the gas-phase selenization reaction is 350°C. At this temperature, the in-plane transition metal sulfides are selenized and transformed into transition metal selenides in the atmosphere of selenium vapor; while the metallic phase molybdenum disulfide will neither be selenized to molybdenum selenide nor transform into a semiconductor phase.

[0021] Another objective of the present invention is to provide a self-supporting electrode based on the transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure prepared by the above-mentioned transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure method, wherein the self-supporting electrode is formed by growing an array of transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure nanosheets on a conductive substrate.

[0022] The method for preparing the self-supporting electrode includes the following specific steps:

[0023] Step 1: Preparation of the transition metal basic carbonate precursor. Specifically, the transition metal salt and an appropriate amount of nucleating agent are dissolved in a mixed solution of water and ethanol, placed in a sealed reactor, and a conductive substrate is added to the mixture. Basic carbonates grown on the conductive substrate are then prepared via a hydrothermal method. The conductive substrate includes pretreated carbon cloth, titanium sheets, and nickel foam; the hydrothermal reaction temperature is 90-140℃, and the reaction time is 5-12 hours.

[0024] Step 2: Preparation of transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, molybdenum trioxide (as molybdenum source), sulfur source, and appropriate amount of reducing agent are mixed with an appropriate amount of water. Simultaneously, the conductive substrate containing basic carbonate nanowire array prepared in Step 1 is placed in the mixture. The mixture is placed in a sealed reactor for hydrothermal reaction to obtain the transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure grown on the conductive substrate. The reaction temperature is 180-240℃, and the reaction time is 8-24h.

[0025] Step 3: Preparation of transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, the conductive substrate with the nanosheet array of transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure obtained in Step 2 is placed in a selenium vapor atmosphere for gas-phase selenization reaction. The reaction temperature of the gas-phase selenization reaction is 300-400℃ and the reaction time is 1-3h.

[0026] Step 4: The conductive substrate sample obtained after the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water and then dried to obtain the self-supporting electrode of the transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure.

[0027] Another objective of this invention is the application of a self-supporting electrode, specifically the application of a transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure self-supporting electrode in the electrocatalytic hydrogen evolution direction.

[0028] This invention provides a method for preparing a self-supporting in-plane heterostructure electrode of transition metal selenide / molybdenum disulfide in metallic phase. The method uses a basic carbonate grown on a conductive substrate as a template, adds a molybdenum source and a sulfur source for further hydrothermal reaction, and rapidly sulfides it. It utilizes the difference in dissolution rates between the transition metal and the molybdenum source during the reaction, as well as defects on the surface of the prepared molybdenum disulfide substrate. During dissolution, cobalt ions may attach to these defect sites and contact the sulfur source in the solution to form transition metal sulfides, successfully preparing a self-supporting in-plane heterostructure electrode of transition metal sulfide / molybdenum disulfide grown on a conductive substrate. The selenization temperature is controlled by utilizing the difference in selenization temperature between transition metals (iron, cobalt, nickel, zinc, etc.) and molybdenum, thereby selectively selenizing the transition metal nanoclusters while retaining the molybdenum disulfide in metallic phase. This synthesis method is simple and easy to operate, and the product is readily available, showing broad prospects.

[0029] In particular, the self-supporting electrode with the cobalt diselenide / metallic molybdenum disulfide in-plane heterostructure exhibited excellent hydrogen evolution performance when used as the anode for electrocatalytic hydrogen evolution, achieving a current density of 10 mA / cm² in 1.0 M potassium hydroxide electrolyte. 2 It exhibits an overpotential of 48 mV, exceeding that of most molybdenum disulfide-based hydrogen evolution catalysts reported to date. Attached Figure Description

[0030] Figure 1 Scanning electron microscope (SEM) image of a self-supporting electrode with an in-plane heterostructure of cobalt diselenide / metallic molybdenum disulfide;

[0031] Figure 2 High-resolution transmission electron microscopy (HRTEM) image of an in-plane heterostructure of cobalt diselenide / metallic molybdenum disulfide;

[0032] Figure 3 Linear voltammetric curves of cobalt diselenide / metallic molybdenum disulfide in-plane heterostructure catalysts and comparative examples in 1.0 M potassium hydroxide.

[0033] Figure 4 Tafel images of cobalt diselenide / metallic molybdenum disulfide in-plane heterostructure catalysts and comparative examples. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] The following specific embodiments provide a detailed description of the specific implementation of the present invention.

[0036] An embodiment of the present invention provides an in-plane heterostructure of transition metal selenide / metallic molybdenum disulfide, wherein the structure uses basic carbonate as a structural template to uniformly embed transition metal selenide nanoclusters within the plane of the metallic molybdenum disulfide, which is coplanar with the metallic molybdenum disulfide, wherein the content of the metallic phase in the molybdenum disulfide is 60-75%; the metallic molybdenum disulfide in this structure has thermal stability.

[0037] In a preferred embodiment of the present invention, the transition metal selenide refers to cobalt selenide, nickel selenide, iron selenide, and zinc selenide. Specifically, the thermal stability of the metallic molybdenum disulfide in the structure refers to the fact that the metallic molybdenum disulfide in the in-plane heterostructure of the precursor transition metal sulfide / metallic molybdenum disulfide undergoes a gas-phase selenization reaction at 350°C without transforming into a semiconductor phase. The aforementioned transition metal selenide / metallic molybdenum disulfide in-plane heterostructure can effectively enhance the hydrogen adsorption capacity of sulfur atoms on the basal surface of the metallic molybdenum disulfide, thereby reducing the overpotential required for the hydrogen evolution reaction and achieving efficient electrochemical hydrogen production.

[0038] An embodiment of the present invention provides a method for preparing an in-plane heterostructure of transition metal selenide / metallic molybdenum disulfide, comprising the following steps:

[0039] Step 1: Preparation of transition metal basic carbonate precursors. Specifically, the transition metal salt and an appropriate amount of nucleating agent are dissolved in a mixed solution of water and ethanol, and the solution is placed in a sealed reaction vessel to prepare basic carbonates via a hydrothermal method. The hydrothermal reaction temperature is 90-140℃, and the reaction time is 5-12 hours.

[0040] Step 2: Prepare a transition metal sulfide / metallic phase molybdenum disulfide in-plane heterostructure. Specifically, take the transition metal basic carbonate prepared in Step 1, weigh out molybdenum trioxide (as a molybdenum source), sulfur source, and an appropriate amount of reducing agent according to the ratio, and add an appropriate amount of water to mix evenly. Place the mixture in a sealed reactor for hydrothermal reaction at a reaction temperature of 180-240℃ for 8-24 hours.

[0041] Step 3: Prepare a transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, place the transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure obtained in Step 2 under a selenium vapor atmosphere for a gas-phase selenization reaction. The reaction temperature of the gas-phase selenization reaction is 300-400℃, and the reaction time is 1-3h.

[0042] Step 4: The transition metal selenide / metal phase molybdenum disulfide powder obtained from the gas-phase selenization reaction in Step 3 is washed with carbon disulfide, ethanol and deionized water respectively and then dried to obtain the product, transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure.

[0043] In a preferred embodiment of the present invention, in step one, the transition metal salt mainly includes cobalt nitrate, nickel nitrate, ferric nitrate, and zinc nitrate, and the nucleating agent includes urea and ammonium fluoride; the sulfur source in step two is selected from one or more of thioacetamide or sodium sulfide, and the reducing agent is selected from any one or more of urea or hydrazine hydrate. The ratio of water to ethanol is 1:1; the ratio of molybdenum atoms in molybdenum trioxide to sulfur atoms in the sulfur source is 1:5-40.

[0044] In a preferred embodiment of the present invention, in step three, the selenium vapor atmosphere is formed by the high-temperature decomposition of selenium powder in an inert atmosphere, which includes pure nitrogen and argon, and the atmosphere should be higher than atmospheric pressure during the reaction.

[0045] The carbon disulfide is used to wash away elemental selenium from the sample surface; the mass ratio of the selenium powder to the in-plane heterostructure powder of transition metal sulfide molybdenum disulfide is 40-100:1.

[0046] In a preferred embodiment of the present invention, in step three, the temperature of the gas-phase selenization reaction is 350°C. At this temperature, the in-plane transition metal sulfides are selenized and transformed into transition metal selenides in the atmosphere of selenium vapor; while the metallic molybdenum disulfide will neither be selenized to molybdenum selenide nor transform into a semiconductor phase.

[0047] An embodiment of the present invention provides a self-supporting electrode based on the transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure prepared by the above-mentioned transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure method. The self-supporting electrode is formed by growing an array of transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure nanosheets on a conductive substrate.

[0048] The method for preparing the self-supporting electrode includes the following specific steps:

[0049] Step 1: Preparation of the transition metal basic carbonate precursor. Specifically, the transition metal salt and an appropriate amount of nucleating agent are dissolved in a mixed solution of water and ethanol, placed in a sealed reactor, and a conductive substrate is added to the mixture. Basic carbonates grown on the conductive substrate are then prepared via a hydrothermal method. The conductive substrate includes pretreated carbon cloth, titanium sheets, and nickel foam; the hydrothermal reaction temperature is 90-140℃, and the reaction time is 5-12 hours.

[0050] Step 2: Preparation of transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, molybdenum trioxide (as molybdenum source), sulfur source, and appropriate amount of reducing agent are mixed with an appropriate amount of water. Simultaneously, the conductive substrate containing basic carbonate nanowire array prepared in Step 1 is placed in the mixture. The mixture is placed in a sealed reactor for hydrothermal reaction to obtain the transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure grown on the conductive substrate. The reaction temperature is 180-240℃, and the reaction time is 8-24h.

[0051] Step 3: Preparation of transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, the conductive substrate with the nanosheet array of transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure obtained in Step 2 is placed in a selenium vapor atmosphere for gas-phase selenization reaction. The reaction temperature of the gas-phase selenization reaction is 300-400℃ and the reaction time is 1-3h.

[0052] Step 4: The conductive substrate sample obtained after the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water and then dried to obtain the self-supporting electrode of the transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure.

[0053] In this embodiment of the invention, the conductive substrate is subjected to ultrasonic treatment with an acid solution and an organic solvent to remove impurities and organic residues, and to transform the hydrophobic surface into a hydrophilic surface. Finally, it is washed with deionized water. Note that after the short ultrasonic treatment, the conductive substrate is stored in deionized water for later use to avoid corrosion. The acid solution is hydrochloric acid or nitric acid solution with a concentration of 3 mol / L. The organic solvent is acetone or ethanol.

[0054] An embodiment of the present invention provides an application of a self-supporting electrode, wherein the self-supporting electrode of the transition metal selenide metal phase molybdenum disulfide in-plane heterostructure is used in the electrocatalytic hydrogen evolution direction.

[0055] The following are specific examples verifying the effectiveness of this method:

[0056] Example 1: A method for preparing an in-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0057] Step 1: Weigh 0.56g of cobalt hexahydrate and 0.78g of urea, dissolve them in 12ml of deionized water, add 12ml of anhydrous ethanol to the solution, and place it in an oven for hydrothermal reaction at 95℃ for 6h to obtain basic cobalt carbonate nanowire array.

[0058] Step 2: Weigh 0.1g of basic cobalt carbonate. Using basic cobalt carbonate as a template, weigh 90mg of molybdenum trioxide, 1.5g of sodium sulfide, 0.45mg of thioacetamide, and 1.8g of urea. Dissolve them in 25ml of deionized water and stir until homogeneous. Place the solution in a 50ml reaction vessel and heat it in an oven at 200℃ for 12 hours.

[0059] Step 3: After the hydrothermal reaction is completed, the product is naturally cooled to room temperature. The solid product is separated and centrifuged, washed several times with deionized water and ethanol, and the solid product is collected and vacuum dried to obtain cobalt sulfide metal phase molybdenum disulfide / in-plane heterostructure powder.

[0060] Step 4: Place the obtained powder in a ceramic boat, and place 200 mg of selenium powder in another ceramic boat. Put them together in a tube furnace, making sure the ceramic boat containing the sample is downstream of the gas flow. Heat at 350°C for 90 minutes in an inert atmosphere (Ar).

[0061] Step 5: The powder obtained from the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water respectively and then dried. The resulting powder is a cobalt diselenide metallic phase molybdenum disulfide basal heterostructure powder.

[0062] Example 2: A method for preparing an in-plane heterostructure of zinc diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0063] Compared to Example 1, cobalt nitrate was replaced with zinc nitrate, otherwise the same as in Example 1.

[0064] Example 3: A method for preparing an in-plane heterostructure of iron diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0065] Compared to Example 1, cobalt nitrate was replaced with ferric nitrate, otherwise the same as in Example 1.

[0066] Example 4: A method for preparing an in-plane heterostructure of nickel diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0067] Compared to Example 1, cobalt nitrate was replaced with nickel nitrate, otherwise the same as in Example 1.

[0068] Example 5: A method for preparing a cobalt diselenide metallic phase molybdenum disulfide in-plane heterostructure self-supporting electrode, comprising the following steps:

[0069] Step 1: Weigh out 0.56g of cobalt hexahydrate and 0.78g of urea, dissolve them in 12ml of deionized water, add 12ml of anhydrous ethanol to the solution, and then add the conductive substrate—carbon cloth (2*2cm). 2The conductive substrate solution was placed in a 50ml reaction vessel and placed in an oven for hydrothermal reaction at 95℃ for 6h to obtain a basic cobalt carbonate nanowire array grown on carbon cloth.

[0070] Step 2: Weigh 90mg of molybdenum trioxide, 1.5g of sodium sulfide, 0.45g of thioacetamide, and 1.8g of urea, dissolve them in 25ml of deionized water and stir until homogeneous. Place the solution in a 50ml reaction vessel, place the basic cobalt carbonate nanowire array grown on carbon cloth obtained in Step 1 in the reaction vessel, and heat it in an oven at 200℃ for 12 hours.

[0071] Step 3: After the hydrothermal reaction is completed, the carbon cloth is naturally cooled to room temperature. The carbon cloth is then removed, washed several times with deionized water and ethanol, and dried under vacuum to obtain an in-plane heterostructure of cobalt sulfide metal phase molybdenum disulfide loaded on the carbon cloth.

[0072] Step 4: Place the obtained carbon cloth sample in a ceramic boat, and place 200 mg of selenium powder in another ceramic boat. Put them together in a tube furnace, making sure the ceramic boat containing the sample is downstream of the gas flow. Heat at 350°C for 90 minutes in an inert atmosphere (Ar).

[0073] Step 5: The carbon cloth sample obtained by the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water respectively and then dried to obtain the self-supporting electrode with the in-plane heterostructure of cobalt diselenide metal phase molybdenum disulfide.

[0074] Example 6: A method for preparing a self-supporting electrode with an in-plane heterostructure of zinc diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0075] Compared to Example 5, zinc nitrate was used instead of cobalt nitrate, otherwise the same as Example 5.

[0076] Example 7: A method for preparing an in-plane heterostructure of iron diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0077] Compared to Example 5, cobalt nitrate was replaced with ferric nitrate, otherwise the same as Example 5.

[0078] Example 8: A method for preparing an in-plane heterostructure of nickel diselenide metallic phase molybdenum disulfide, comprising the following steps:

[0079] Compared to Example 5, cobalt nitrate was replaced with nickel nitrate, otherwise the same as Example 5.

[0080] Comparative Example 1: A method for preparing a self-supporting electrode of cobalt selenide grown on carbon cloth, comprising the following steps:

[0081] Step 1: Weigh out 0.56g of cobalt hexahydrate and 0.78g of urea, dissolve them in 12ml of deionized water, add 12ml of anhydrous ethanol to the solution, and then add the conductive substrate—carbon cloth (2*2cm). 2 The conductive substrate solution was placed in a 50ml reaction vessel and then placed in an oven for hydrothermal reaction at 95℃ for 6 hours to obtain a basic cobalt carbonate nanowire array grown on carbon cloth.

[0082] Step 2: Weigh 1.5g of sodium sulfide, 0.45g of thioacetamide, and 1.8mg of urea, dissolve them in 25ml of deionized water and stir until homogeneous. Place the solution in a 50ml reaction vessel, place the basic cobalt carbonate nanowire array grown on carbon cloth obtained in Step 1 in the reaction vessel, and heat it in an oven at 200℃ for 12 hours.

[0083] Step 3: After the hydrothermal reaction is completed, the carbon cloth is naturally cooled to room temperature. The carbon cloth is then removed, washed several times with deionized water and ethanol, and dried under vacuum to obtain cobalt disulfide loaded on the carbon cloth.

[0084] Step 4: Place the obtained carbon cloth sample in a ceramic boat, and place 200 mg of selenium powder in another ceramic boat. Put them together in a tube furnace, making sure the ceramic boat containing the sample is downstream of the gas flow. Heat at 350°C for 90 minutes in an inert atmosphere (Ar).

[0085] Step 5: The carbon cloth sample obtained by the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water respectively and then dried to obtain the cobalt diselenide self-supporting electrode.

[0086] Comparative Example 2: A method for preparing a self-supporting electrode of molybdenum disulfide grown on carbon cloth, comprising the following steps:

[0087] Step 1: Weigh 90mg of molybdenum trioxide, 1.5g of sodium sulfide, 0.45g of thioacetamide, and 1.8g of urea, dissolve them in 25ml of deionized water and stir until homogeneous. Place the solution in a 50ml reaction vessel, place the basic cobalt carbonate nanowire array grown on carbon cloth obtained in Step 1 in the reaction vessel, and heat it in an oven at 200℃ for 12 hours.

[0088] Step 2: After the hydrothermal reaction is completed, the carbon cloth is naturally cooled to room temperature. The carbon cloth is then removed, washed several times with deionized water and ethanol, and then vacuum dried to obtain the in-plane heterostructure of molybdenum disulfide metal phase supported on the carbon cloth.

[0089] Comparative Example 3: A method for fabricating a self-supporting electrode with an out-of-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide grown on carbon cloth, comprising the following steps:

[0090] Step 1: Repeat Comparative Example 2 to obtain a self-supporting metal phase molybdenum disulfide electrode;

[0091] Step 2: Cobalt hydroxide nanoparticles were deposited on molybdenum disulfide nanosheets. In a standard three-electrode electrochemical cell, an out-of-plane heterostructure of cobalt hydroxide and molybdenum disulfide grown on carbon cloth was obtained using a chronoamperometry method. The resulting self-supported molybdenum disulfide electrode, graphite rod, and Ag / AgCl (saturated KCl solution) were used as the working electrode, counter electrode, and reference electrode, respectively. A 0.1M aqueous solution of cobalt nitrate was used as the electrolyte. The reaction potential was -1.5V, and the reaction time was 120s.

[0092] Step 3: After electrodeposition, the electrode is rinsed several times with deionized water and dried overnight at 40°C;

[0093] Step 4: Place the carbon cloth sample in a ceramic boat and place 200mg of selenium powder in another ceramic boat. Put them together in a tube furnace, making sure the ceramic boat containing the sample is downstream of the gas flow. Heat at 350℃ for 90 minutes in an inert atmosphere (Ar).

[0094] Step 5: The carbon cloth sample obtained by the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water respectively and then dried to obtain the self-supporting electrode of the cobalt diselenide metal phase molybdenum disulfide out-of-plane heterostructure.

[0095] Experimental results:

[0096] The self-supporting electrode with an in-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide prepared in Example 5 was characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Figure 1 SEM images of a self-supporting electrode with an in-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide at different magnifications are shown. Figure 2 HRTEM images of the in-plane heterostructure of molybdenum disulfide corresponding to the cobalt diselenide metallic phase are shown.

[0097] The self-supporting electrode with an in-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide prepared in Example 5, along with the self-supporting electrode with cobalt diselenide in Comparative Example 1, the self-supporting electrode with molybdenum disulfide metallic phase in Comparative Example 2, and the self-supporting electrode with an out-of-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide in Comparative Example 3, were used as working electrodes in 1M KOH solution for electrochemical hydrogen evolution reaction. Figure 3 These correspond to the linear sweep voltammetry curves of these self-supporting electrodes. From Figure 3 As can be seen from the data, the self-supported electrode with an in-plane heterostructure of cobalt diselenide metallic phase molybdenum disulfide exhibits excellent catalytic activity in alkaline solution, with a value of 10 mA / cm². 2The overpotential corresponding to the current density is used as the evaluation parameter. The overpotential corresponding to the cobalt diselenide / molybdenum disulfide in-plane heterostructure self-supporting electrode is 48 mV. This performance is comparable to that of currently reported advanced water electrolysis hydrogen evolution catalysts. In the figure, CoSe2 / CC, CoSe2 / 1T-MoS2 / CC, 1T-MoS2 / CC, and CoSe2@1T-MoS2 / CC are cobalt diselenide, cobalt diselenide / molybdenum disulfide out-of-plane heterostructure, molybdenum disulfide in-plane heterostructure, and cobalt diselenide / molybdenum disulfide in-plane heterostructure self-supporting electrodes, respectively.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a transition metal selenide / metallic molybdenum disulfide in-plane heterostructure, characterized in that, Includes the following steps: Step 1: Preparation of transition metal basic carbonates. Specifically, the transition metal salt and an appropriate amount of nucleating agent are dissolved in a mixed solution of water and ethanol, and the solution is placed in a sealed reaction vessel. The basic carbonates are then synthesized via a hydrothermal method. The hydrothermal reaction temperature is 90-140 ℃, and the reaction time is 5-12 h. The transition metal basic carbonates include: basic iron carbonate, basic cobalt carbonate, basic nickel carbonate, and basic zinc carbonate. The nucleating agents include: urea and ammonium fluoride. Step 2: Preparation of transition metal sulfide / metallic phase molybdenum disulfide in-plane heterostructure. Specifically, the transition metal basic carbonate prepared in Step 1 is weighed, and molybdenum trioxide, sulfur source, and appropriate amount of reducing agent are added according to the ratio. An appropriate amount of water is added and mixed thoroughly. The mixture is placed in a sealed reactor for hydrothermal reaction at a temperature of 180-240 ℃ for 8-24 h. The sulfur source is selected from one or more of thioacetamide or sodium sulfide; the reducing agent is selected from any one or more of urea or hydrazine hydrate. Step 3: Prepare a transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, place the transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure obtained in Step 2 under a selenium vapor atmosphere for a gas-phase selenization reaction. The reaction temperature of the gas-phase selenization reaction is 300-400 ℃, and the reaction time is 1-3 h. Step 4: The transition metal selenide / metal phase molybdenum disulfide powder obtained from the gas-phase selenization reaction in Step 3 is washed with carbon disulfide, ethanol and deionized water and then dried. The resulting sample is an in-plane heterostructure of transition metal selenide / metal phase molybdenum disulfide.

2. The method for preparing the transition metal selenide / metallic molybdenum disulfide in-plane heterostructure according to claim 1, characterized in that, In step one, the ratio of water to ethanol is 1:1; In step two, the ratio of the number of molybdenum atoms in the molybdenum trioxide to the number of sulfur atoms in the sulfur source is 1:5-40.

3. The method for preparing the transition metal selenide / metallic molybdenum disulfide in-plane heterostructure according to claim 2, characterized in that, In step three, the selenium vapor atmosphere is formed by the high-temperature decomposition of selenium powder in an inert atmosphere, which includes pure nitrogen and argon. The atmosphere should be higher than atmospheric pressure during the reaction. The carbon disulfide is used to wash away elemental selenium from the sample surface; the mass ratio of the selenium powder to the in-plane heterostructure powder of transition metal sulfide molybdenum disulfide is 40-100:

1.

4. The method for preparing the transition metal selenide / metallic molybdenum disulfide in-plane heterostructure according to claim 2, characterized in that, In step three, the temperature of the gas-phase selenization reaction is 350 °C.

5. A self-supporting electrode, characterized in that, The transition metal selenide / molybdenum disulfide in-plane heterostructure obtained by the preparation method of any one of claims 1-4 is wherein the self-supporting electrode is formed by growing an array of transition metal selenide / molybdenum disulfide in-plane heterostructure nanosheets on a conductive substrate.

6. The self-supporting electrode according to claim 5, characterized in that, The method for preparing the self-supporting electrode includes the following specific steps: Step 1: Preparation of transition metal basic carbonate precursor. Specifically, the transition metal salt and an appropriate amount of nucleating agent are dissolved in a mixed solution of water and ethanol, placed in a sealed reactor, and a conductive substrate is added to the mixture. Basic carbonate grown on the conductive substrate is prepared by hydrothermal method. The conductive substrate includes pretreated carbon cloth, titanium sheet, and nickel foam. The hydrothermal reaction temperature is 90-140 ℃, and the reaction time is 5-12 h. Step 2: Preparation of transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, molybdenum trioxide, sulfur source, and appropriate amount of reducing agent are mixed with an appropriate amount of water. Simultaneously, the conductive substrate containing basic carbonate nanowire array prepared in Step 1 is placed in the mixture. The mixture is placed in a sealed reactor for hydrothermal reaction to obtain the transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure grown on the conductive substrate. The reaction temperature is 180-240 ℃, and the reaction time is 8-24 h. Step 3: Preparation of transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure. Specifically, the conductive substrate with the nanosheet array of transition metal sulfide / metal phase molybdenum disulfide in-plane heterostructure obtained in Step 2 is placed in a selenium vapor atmosphere for gas phase selenization reaction. The reaction temperature of the gas phase selenization reaction is 300-400 ℃ and the reaction time is 1-3 h. Step 4: The conductive substrate sample obtained after the gas-phase selenization reaction is washed with carbon disulfide, ethanol and deionized water and then dried to obtain the self-supporting electrode of the transition metal selenide / metal phase molybdenum disulfide in-plane heterostructure.

7. An application of a self-supporting electrode, based on the self-supporting electrode of claim 6, characterized in that, The application is to use the self-supporting electrode for the electrocatalytic hydrogen evolution reaction.

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