Electrolytic water hydrogen production catalyst, preparation method and application thereof

Abstract

The present application relates to a kind of hydrogen catalyst for electrolysis of water and its preparation method and application, belong to the technical field of hydrogen production by electrolysis of water, at least solve one of the following technical problems: (1) the intrinsic catalytic activity of existing two-dimensional transition metal chalcogenide (TMDs) as hydrogen production by electrolysis of water catalyst is low;(2) the grain boundary quality of catalyst obtained by the preparation method of existing TMDs hydrogen production by electrolysis of water catalyst is poor, it is difficult to form high catalytic activity twin grain boundary.The hydrogen catalyst for electrolysis of water includes transition metal selenide, the grain boundary in the transition metal selenide is all twin grain boundary with 60° rotation angle, the twin grain boundary is composed of four-membered ring and eight-membered ring, the density of the twin grain boundary is 10 4 -10 10 cm ‑2 . The grain boundary quality of the hydrogen catalyst for electrolysis of water is high, and the catalytic activity is good.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, and in particular to a water electrolysis catalyst, its preparation method, and its application. Background Technology

[0002] Compared to other clean energy sources such as wind, hydro, and solar power, hydrogen energy has many advantages, including good thermal conductivity, relatively high calorific value and energy density, less susceptibility to weather conditions, and zero carbon dioxide emissions, and is widely recognized as the most suitable energy carrier to replace traditional fossil fuels. Hydrogen production through water electrolysis, compared to hydrogen production from fossil fuels, is a green, efficient, large-scale, and sustainable process for energy conversion and storage.

[0003] Two-dimensional transition metal chalcogenides (TMDs) not only possess perfect crystal lattices, but the grain boundaries in polycrystalline thin films, acting as typical one-dimensional defects, can induce intrinsic activation of the two-dimensional basal planes, exhibiting excellent electrocatalytic activity. Notably, the enhanced electrocatalytic performance is closely related to grain boundary engineering parameters such as atomic type, dislocation nucleus structure, density, and crystal orientation. For example, twin boundaries rich in eight-membered rings are considered to possess the best electrocatalytic hydrogen evolution activity.

[0004] When using two-dimensional transition metal chalcogenides (such as transition metal selenides) as catalysts for water electrolysis to produce hydrogen, existing methods mainly involve chemical vapor deposition (CVD), where the metal source undergoes a vaporization and redeposition process. However, due to the rapid gas kinetics and the diversity of chemical phases involved in the reaction, existing methods often result in poor grain boundary quality in water electrolysis catalysts, and it is difficult to form highly active twin boundaries. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a water electrolysis hydrogen production catalyst and its preparation method and application, which can at least solve one of the following technical problems: (1) Existing two-dimensional transition metal chalcogenides (TMDs) have low intrinsic catalytic activity and poor grain boundary quality as water electrolysis hydrogen production catalysts; (2) The TMDs water electrolysis hydrogen production catalysts prepared by existing preparation methods have poor grain boundary quality and it is difficult to form highly catalytically active twin boundaries.

[0006] On one hand, the present invention provides a catalyst for hydrogen production through water electrolysis, the catalyst comprising a transition metal selenide, wherein all grain boundaries within the transition metal selenide are twin boundaries with a rotation angle of 60°, the twin boundaries being composed of four-membered rings and eight-membered rings, and the density of the twin boundaries being 10. 4 -10 10 cm -2 .

[0007] Preferably, the content of octagons in the twin boundaries is 33-60%.

[0008] Preferably, the transition metal is molybdenum or tungsten.

[0009] Preferably, the four-membered rings and eight-membered rings in the twin boundary are arranged at irregular or regular intervals.

[0010] On the other hand, the present invention provides a method for preparing a water electrolysis hydrogen production catalyst, for preparing the above-mentioned water electrolysis hydrogen production catalyst, the preparation method comprising:

[0011] (1) Dissolve the transition metal salt and strong base in water to obtain the precursor solution;

[0012] (2) Spin-coating the precursor solution onto the substrate;

[0013] (3) Place the substrate in the middle of the tubular furnace, place the selenium powder at the gas inlet end of the tubular furnace, evacuate the tubular furnace and fill it with reducing gas and inert gas, heat it to sublimate the selenium powder, and then react and anneal it with the precursor solution.

[0014] (4) Spin-coat the PMMA solution onto the surface of the transition metal selenide, dry it and then put it into the NaOH aqueous solution. After the transition metal selenide is detached from the surface of the growth substrate, use a substrate with electrodes to pick it up, dry it, and wash off the PMMA on the surface of the transition metal selenide. Finally, transfer the transition metal selenide from the growth substrate to the substrate.

[0015] Preferably, the preparation method further includes step (5): covering the entire device with a PMMA film, and then removing the PMMA above the region of interest in the transition metal selenide nanosheet with EBL, with the exposed portion of the transition metal selenide serving as a catalyst.

[0016] Preferably, the mass ratio of the transition metal salt to the strong base is 1-10:2.

[0017] Preferably, the substrate is a sapphire substrate or a SiO2 / Si substrate.

[0018] Preferably, in step (3), the heating includes: the middle part of the tubular furnace is heated to 700-800°C at a rate of 40-50°C / min and then held for 1-10 minutes, and the air inlet end of the tubular furnace is heated to 300-350°C at a rate of 40-50°C / min and then held for 1-10 minutes.

[0019] Thirdly, the present invention also provides the application of the above-mentioned water electrolysis hydrogen production catalyst and the water electrolysis hydrogen production catalyst obtained by the above preparation method in water electrolysis hydrogen production.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. The rotation angle of the grain boundaries in existing water electrolysis hydrogen production catalysts is completely random and not a specific 60° grain boundary with 4 / 8-membered rings (four-membered rings and eight-membered rings). However, the grain boundaries inside the water electrolysis hydrogen production catalyst of this invention are all uniform 60° grain boundaries, that is, twin boundaries. The twin boundaries are composed of 4 / 8-membered rings (four-membered rings and eight-membered rings), with high grain boundary quality and high twin boundary density, resulting in good catalytic activity.

[0022] 2. Strong bases adsorb onto the surface of selenides during the preparation of hydrogen production catalysts via water electrolysis, protecting the selenides and resulting in high-quality selenides with high twin boundary density.

[0023] 3. The rotation angle of the grain boundaries in the electrolytic hydrogen production catalyst prepared by existing methods is completely random and not a specific 60° grain boundary with 4 / 8 rings. However, the grain boundaries inside the transition metal selenide prepared by the method of this invention are uniform 60° grain boundaries, that is, twin boundaries. Twin boundaries are composed of 4 / 8 rings and have good catalytic activity.

[0024] 4. In this invention, molybdenum salt or tungsten salt is directly spin-coated onto the substrate surface as a metal source. The metal source on the substrate surface diffuses to form a high density of nucleation sites. Furthermore, the growth of selenides at different nucleation sites on the substrate surface is influenced by capillary forces, forming a high density of twin boundaries. These capillary forces cause adjacent domains to rotate and share a straight edge, forming twin boundaries. Combined with the high density of nucleation sites, this ultimately results in a high density (10) 4 -10 10 cm -2 Twin boundaries.

[0025] 5. The preparation method of the electrolytic water hydrogen production catalyst of the present invention directly spin-coates molybdenum salt or tungsten salt onto the substrate surface as a metal source, and then allows selenium to react with the metal source, avoiding the metal source vaporization and re-deposition process in the prior art. The method of the present invention can precisely control the grain boundary density: when the precursor solution (metal source) is spin-coated onto the substrate surface, at temperatures below the evaporation temperature of the metal source, many nucleation sites will be generated on the substrate surface, forming high-density grain boundaries; when the annealing temperature is increased above the evaporation temperature of the metal source, the metal source will evaporate from the substrate surface into the air, reducing the nucleation site density on the substrate surface, thereby reducing the grain boundary density.

[0026] 6. The high density and high quality twin boundaries inside the water electrolysis hydrogen production catalyst prepared by this invention have excellent electrocatalytic performance and good catalytic activity in electrocatalytic hydrogen production, and can be used as a catalyst for electrocatalytic hydrogen production.

[0027] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1a An optical microscope image of molybdenum diselenide from Example 1;

[0030] Figure 1b Here is an SHG image of molybdenum diselenide from Example 1;

[0031] Figure 2 Dark-field TEM image of molybdenum diselenide from Example 1;

[0032] Figure 3 An atomic force microscope image of molybdenum diselenide from Example 1;

[0033] Figure 4a The Raman spectrum of molybdenum diselenide in Example 1 is shown below.

[0034] Figure 4b The image shows the Raman mapping of molybdenum diselenide from Example 1.

[0035] Figure 5 This is a high-magnification STEM image of molybdenum diselenide from Example 1;

[0036] Figure 6 Here is a HER image of molybdenum diselenide from Example 1;

[0037] Figure 7a Here is an SHG image of molybdenum diselenide from Example 2;

[0038] Figure 7b Here is an SHG image of molybdenum diselenide from Example 3;

[0039] Figure 7c SHG image of molybdenum diselenide in Comparative Example 2;

[0040] Figure 8a An optical microscope image of tungsten diselenide from Example 4;

[0041] Figure 8b This is an SHG image of tungsten diselenide from Example 4. Detailed Implementation

[0042] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0043] Existing methods for growing hydrogen production catalysts through water electrolysis mainly involve chemical vapor deposition (CVD). The metal source undergoes a vaporization and redeposition process. However, due to the rapid gas dynamics and the diversity of chemical phases involved in the reaction, the rotation angle of grain boundaries prepared by existing methods is completely random and not a specific 60° grain boundary with 4 / 8 rings (non-60° grain boundaries are composed of 5 / 7-membered rings, while 60° grain boundaries are composed of 4 / 8-membered rings, and 60° grain boundaries containing 4 / 8-membered rings have higher catalytic activity). In addition, the grain boundary density is affected by the nucleation density, and controlling the nucleation density in CVD methods is difficult.

[0044] Therefore, this invention provides a catalyst for hydrogen production through water electrolysis, the catalyst comprising a transition metal selenide, wherein all grain boundaries within the transition metal selenide are twin boundaries with a rotation angle of 60°, the twin boundaries being composed of four-membered rings and eight-membered rings, and the density of the twin boundaries being 10. 4 -10 10 cm -2 For example, 10 4 cm -2 10 5 cm -2 10 6 cm -2 10 7 cm -2 10 8 cm -2 10 9 cm -2 10 10 cm -2 ; Further preferred is 10 6 -10 10 cm -2 The high density of twin boundaries gives the water electrolysis hydrogen production catalyst better catalytic activity. The density of twin boundaries refers to the number of grain boundaries per unit area.

[0045] The rotation angle of the grain boundaries in existing water electrolysis hydrogen production catalysts is completely random, not a specific 60° grain boundary with 4 / 8-membered rings (four-membered rings and eight-membered rings). However, the grain boundaries inside the water electrolysis hydrogen production catalyst of this invention are all uniform 60° grain boundaries, that is, twin boundaries. The twin boundaries are composed of 4 / 8-membered rings (four-membered rings and eight-membered rings), and the twin boundary density is high, resulting in good catalytic activity.

[0046] Furthermore, the four-membered rings and eight-membered rings are arranged at irregular or regular intervals.

[0047] Furthermore, the content of octagonal rings in the twin boundaries is 33-60%, for example, 33%, 35%, 40%, 45%, 50%, 55%, and 60%. Octagonal rings have better catalytic activity due to their increased number of exposed atomic sites; therefore, the higher the content of octagonal rings, the better the catalytic activity of the catalyst. The water electrolysis hydrogen production catalyst of the present invention has a high content of octagonal rings, thus exhibiting better catalytic performance.

[0048] For example, the transition metal is molybdenum or tungsten.

[0049] For example, the water electrolysis hydrogen production catalyst is hexagonal or triangular.

[0050] Furthermore, the transition metal selenide has a single-layer thickness.

[0051] On the other hand, the present invention provides a method for preparing a water electrolysis hydrogen production catalyst, for preparing the above-mentioned water electrolysis hydrogen production catalyst, the preparation method comprising:

[0052] (1) Dissolve the transition metal salt and strong base in water to obtain the precursor solution;

[0053] (2) Spin-coating the precursor solution onto the substrate;

[0054] (3) Place the substrate in the middle of the tubular furnace, place the selenium powder at the gas inlet end of the tubular furnace, evacuate the tubular furnace and fill it with reducing gas and inert gas, heat it to sublimate the selenium powder, and then react and anneal it with the precursor solution.

[0055] (4) Spin-coat the PMMA solution onto the surface of the transition metal selenide, dry it and then put it into the NaOH aqueous solution. After the transition metal selenide is detached from the surface of the growth substrate, use a substrate with electrodes to pick it up, dry it, and wash off the PMMA on the surface of the transition metal selenide. Finally, transfer the transition metal selenide from the growth substrate to the substrate.

[0056] Compared with existing technologies, the grain boundary rotation angle of the water electrolysis hydrogen production catalyst prepared by existing methods is completely random, not a specific 60° grain boundary with 4 / 8 rings. In contrast, the transition metal selenide prepared by the method of this invention has uniform 60° grain boundaries, i.e., twin boundaries, composed of 4 / 8 rings. Furthermore, the twin boundary density is high, the content of eight-membered rings is high, resulting in excellent crystal quality and good catalytic activity. Strong bases adsorb onto the selenide surface during the preparation of the water electrolysis hydrogen production catalyst, protecting the selenide and thus resulting in high-quality selenide and high twin boundary density. This invention directly spin-coats molybdenum salt or tungsten salt onto the substrate surface as a metal source. The metal source on the substrate surface diffuses to form a high-density nucleation site. The growth of selenide at different nucleation sites on the substrate surface is affected by capillary forces, forming a high-density twin boundary. The capillary force causes adjacent crystal domains to rotate and share a straight edge, forming a twin boundary. Combined with the high-density nucleation site, a high-density (10) twin boundary is ultimately formed. 4 -10 10 cm -2 The method of this invention can precisely control the grain boundary density: a precursor solution (metal source) is spin-coated onto the substrate surface. When the temperature is below the evaporation temperature of the metal source, many nucleation sites will be generated on the substrate surface, forming high-density grain boundaries. When the annealing temperature is increased above the evaporation temperature of the metal source, the metal source will evaporate from the substrate surface into the air, and the nucleation site density on the substrate surface will decrease, thereby reducing the grain boundary density.

[0057] Specifically, the preparation method further includes step (5): covering the entire device with a 500 nm PMMA film, and then removing the PMMA above the region of interest in the transition metal selenide nanosheet using EBL, with the exposed portion of the transition metal selenide serving as a catalyst. The region of interest refers to the region containing twin boundaries.

[0058] In this invention, the transition metal salt is used as a metal source. Exemplarily, the transition metal salt is an inorganic molybdenum salt or an inorganic tungsten salt, such as ammonium molybdate or ammonium tungstate. When ammonium molybdate is used, the generated water electrolysis hydrogen production catalyst is molybdenum diselenide, which has a regular hexagonal shape. When ammonium tungstate is used, the generated water electrolysis hydrogen production catalyst is tungsten diselenide, which has an equilateral triangular shape.

[0059] For example, the strong base is sodium hydroxide and / or potassium hydroxide.

[0060] In this invention, if the amount of strong alkali used is too low, it will lead to the formation of multiple layers; if the amount of strong alkali used is too high, it will etch the product. Preferably, the mass ratio of the transition metal salt to the strong alkali is 1-10:2.

[0061] In step (1), a transparent and clear precursor solution is obtained by stirring while dissolving the transition metal salt and strong base in water.

[0062] For example, the substrate is a sapphire substrate or a SiO2 / Si substrate.

[0063] In this invention, the substrate does not need to be treated to be hydrophilic; moderate hydrophilicity is sufficient. If the hydrophilicity is too high, a large amount of transition metal precursor will be spin-coated onto the substrate surface, resulting in multiple layers of the final selenide. If the hydrophilicity is poor, the transition metal precursor will not be able to be coated onto the substrate because the precursor solution is aqueous.

[0064] For example, the precursor solution includes 5-10 mmol / L ammonium molybdate, 0.5-1 mol / L NaOH or KOH.

[0065] To promote the growth of the hydrogen production catalyst through water electrolysis, i.e., to ensure the smooth progress of the reaction, preferably, in step (3), the heating includes: raising the temperature of the middle part of the tubular furnace to 700-800°C at a rate of 40-50°C / min and holding it for 1-10 minutes. More preferably, raising the temperature of the middle part of the tubular furnace to 730-750°C at a rate of 40-50°C / min and holding it for 1-10 minutes is beneficial for the formation of high-density twin boundaries.

[0066] Selenium powder is placed at the gas inlet end of the tubular furnace of the present invention. In order to sublimate the selenium powder, preferably, in step (3), the heating further includes: heating the gas inlet end of the tubular furnace to 300-350°C at a rate of 40-50°C / min and holding it for 1-10 minutes. After sublimation, the selenium powder enters the middle of the tubular furnace and reacts with the metal source on the substrate.

[0067] In this invention, the reducing gas is used to reduce transition metals and promote the formation of transition metal selenides, while the inert gas acts as a carrier gas to transport the reducing gas. The reducing gas and inert gas are input from the inlet of the tubular furnace, carrying the sublimated selenium into the middle of the furnace, whereby the selenium reacts with the metal source on the substrate to form transition metal selenides.

[0068] For example, in step (3), the reducing gas is hydrogen and the inert gas is argon.

[0069] To promote the growth of high-quality twin boundaries, preferably, the volume ratio of the reducing gas to the inert gas is 5:95-10:90.

[0070] After the reaction and annealing are completed, allow it to cool naturally.

[0071] In step (4), specifically, the step of transferring the reaction-generated transition metal selenide from the substrate to the substrate with electrodes includes:

[0072] (a) Spin-coat the PMMA solution onto the surface of the transition metal selenide at a speed of 3000 r / min and dry at 80 degrees Celsius for 10 min.

[0073] (b) Place the dried substrate into a 2M NaOH aqueous solution. After the transition metal selenide detaches from the surface of the growth substrate, retrieve it with a substrate with electrodes.

[0074] (c) The retrieved substrate is dried at 80 degrees Celsius for 8 minutes, and then PMMA on the surface of the transition metal selenide is removed with acetone. Finally, the transition metal selenide is transferred from the growth substrate to the substrate.

[0075] Thirdly, the present invention also provides the application of the above-mentioned water electrolysis hydrogen production catalyst and the water electrolysis hydrogen production catalyst obtained by the above preparation method in water electrolysis hydrogen production.

[0076] This water electrolysis hydrogen production catalyst exhibits good catalytic activity in electrocatalytic hydrogen production. At 10 mA / cm², 2 At current densities, the hydrogen evolution overpotential of this catalyst is 195-380 mV, and the Tafel slope is 70-150 mV dec. -1 .

[0077] The transition metal selenides and their preparation methods of the present invention will be further illustrated below through specific embodiments.

[0078] Example 1

[0079] (1) Take 0.05g of ammonium molybdate tetrahydrate and 0.05g of potassium hydroxide respectively, dissolve them in 5mL of ultrapure water, and stir ultrasonically for 5 minutes each to make the solution clear and transparent, thus obtaining the precursor solution of molybdenum;

[0080] (2) Take a 1cm×1cm Si / SiO2 substrate and rinse the substrate surface with nitrogen gas. Place the cleaned Si / SiO2 substrate on a spin coater, set the rotation speed to 8000rpm / s and the spin coating time to 30 seconds. After the substrate reaches the maximum rotation speed, drop the precursor solution onto the surface of the Si / SiO2 substrate to spread the solution evenly.

[0081] (3) After spin coating, place the Si / SiO2 substrate coated with the precursor solution in a clean ceramic boat, and then place the ceramic boat in the center of a tube furnace; place 0.1g of selenium powder at one end of the tube furnace inlet (i.e., the inlet end), evacuate the furnace, and then fill it with argon gas (maintaining a 5% volume concentration of H2 / Ar gas during heating and cooling); set the tube furnace heating program: the heating rate at the center of the tube furnace is 50℃ per minute, and the temperature is maintained at 740℃ for 3 minutes (i.e., the reaction and annealing process); the heating rate at the location where the selenium powder is placed is 40℃ per minute, and the temperature is maintained at 300℃ for 3 minutes; after completion, allow it to cool naturally. High-quality molybdenum diselenide containing high-density twin boundaries is obtained on the surface of the Si / SiO2 substrate. The molybdenum diselenide exhibits a hexagonal morphology, such as... Figure 1a As shown.

[0082] The polarized SHG image shown in Figure 1(b) proves that there are a large number of 60° grain boundaries inside the molybdenum diselenide prepared in Example 1;

[0083] like Figure 2 The dark-field TEM image shown proves that the grain boundaries inside the molybdenum diselenide prepared in Example 1 are uniform 60° grain boundaries, which are twin boundaries.

[0084] like Figure 3 The AFM diagram shown demonstrates that the molybdenum diselenide prepared in Example 1 has a single-layer thickness. The single-layer thickness is the thinnest thickness of a layered material. Single-layer materials have a special direct band gap and can save space in devices.

[0085] like Figure 4a The characteristic peaks of the Raman spectrum shown prove that the material grown in Example 1 is molybdenum diselenide;

[0086] like Figure 4b The Raman mapping images shown demonstrate that the molybdenum diselenide prepared in Example 1 has excellent optical uniformity;

[0087] like Figure 5 The high-magnification scanning transmission electron microscope images shown indicate that the twin boundaries in the molybdenum diselenide prepared in Example 1 consist of 4 / 8 rings (marked in the figure), exhibiting excellent crystallinity.

[0088] The density of twin boundaries is 10. 8 cm -2 The content of octet rings was 44%.

[0089] Molybdenum diselenide was used in a four-electrode system micro water electrolysis hydrogen evolution battery as a catalyst for electrocatalytic hydrogen evolution. Figure 6 It can be seen that the molybdenum diselenide prepared in Example 1 has excellent electrocatalytic performance at a potential of 10 mA / cm². 2At this time, the potential of molybdenum diselenide is only 190mV, which gives it good electrocatalytic hydrogen evolution performance.

[0090] Example 2

[0091] Molybdenum diselenide was prepared according to the method of Example 1, except that the temperature in the tube furnace was maintained at 770°C for 3 minutes. As shown in Figure 7(a), the grain boundary density inside the molybdenum diselenide grown in Example 2 was lower than that in Example 1. The twin boundary density was 10-1. 5 cm -2 The content of octet rings is 35%.

[0092] Example 3

[0093] Molybdenum diselenide was prepared according to the method of Example 1, except that the temperature in the tube furnace was maintained at 800°C for 3 minutes. As shown in Figure 7(b), the grain boundary density inside the molybdenum diselenide grown in Example 3 was further reduced compared to Example 2. The twin boundary density was 10-1. 4 cm -2 The content of octagonal rings is 33%.

[0094] As can be seen from the comparison of Examples 1-3, the preparation method of the present invention can precisely control the density of grain boundaries by controlling the reaction temperature.

[0095] Example 4

[0096] Molybdenum diselenide was prepared according to the method of Example 1, except that 0.05 g of ammonium tungstate was used instead of 0.05 g of ammonium molybdate tetrahydrate. Figure 8a and Figure 8b As shown, the tungsten diselenide grown in Example 5 contains a high density of twin boundaries. The density of the twin boundaries is 10-1. 8 cm -2 The content of octet rings is 40%.

[0097] Comparative Example 1

[0098] Molybdenum diselenide was prepared using an existing vapor-phase precipitation method. The steps included: using 0.03 g of molybdenum trioxide as the molybdenum source and 0.05 g of selenium powder as the selenium source. A clean silica substrate was placed on top of the molybdenum oxide. After the molybdenum trioxide was vaporized at 800°C, it was deposited onto the substrate surface and reacted with selenium vapor to grow MoSe2. The twin boundary density was 10. 2 cm -2 The content of octetral rings is 25%.

[0099] Comparative Example 2

[0100] Molybdenum diselenide was prepared according to the method of Example 1, except that potassium hydroxide was not added to the precursor solution in step (1). As shown in Figure 7(c), a single hexagonal molybdenum diselenide morphology contains only six grain boundaries. This indicates that the addition of a strong base can increase the density of twin boundaries. The density of twin boundaries is 10. 3 cm -2 The content of octet rings is 30%.

[0101] Catalytic performance testing: The molybdenum diselenide prepared in Examples 1-4 and Comparative Examples 1-2, as well as the single-crystal MoSe2 without grain boundaries purchased from Zhongke Leiming (Beijing) Technology Co., Ltd., were used to prepare microcells for electrocatalytic hydrogen evolution performance (HER). The testing methods are as follows:

[0102] (1) First, the device was fabricated by transferring a monolayer of molybdenum diselenide onto a clean Si / SiO2 (300 nm thick SiO2) substrate using a PMMA film. Then, two gold electrodes were deposited on a molybdenum diselenide nanosheet using an electron beam. Subsequently, the entire device was covered with a 500 nm PMMA film. Then, the PMMA above the region of interest in the molybdenum diselenide nanosheet was removed by EBL. The exposed molybdenum diselenide was used as a catalyst for HER testing.

[0103] (2) The HER performance of molybdenum diselenide was tested using a four-electrode system with 0.5 M H2SO4 as the electrolyte and the scan rate set to 5 mV per step.

[0104] (3) During the test, the relationship between the current density and voltage of the test samples was used to demonstrate that the sample of Example 1, which had the highest grain boundary density, exhibited the best electrocatalytic activity. Figure 6 As shown in Table 1, at 10 mA / cm 2 At the given current density, the overpotential of Example 1 is 195 mV, exceeding that of Examples 2-4, which have lower grain boundary densities. This is because the eight-membered rings in the twin boundaries exhibit excellent electrocatalytic activity, such as... Figure 5 As shown, the high density of twin boundaries can greatly promote the catalytic effect of molybdenum diselenide substrates on electrocatalytic hydrogen evolution.

[0105] Table 1

[0106] Example 1 195mV <![CDATA[70mV dec -1 ]]> Example 2 260mV <![CDATA[77mV dec -1 ]]> Example 3 380mV <![CDATA[150mV dec -1 ]]> Example 4 200mV <![CDATA[70mV dec -1 ]]> <![CDATA[Commercially available MoSe2]]> 600mV <![CDATA[180mV dec -1 ]]> Comparative Example 1 500mV <![CDATA[160mV dec -1 ]]> Comparative Example 2 480mV <![CDATA[160mV dec -1 ]]>

[0107] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A catalyst for hydrogen production by water electrolysis, characterized in that, The water electrolysis hydrogen production catalyst comprises a transition metal selenide, wherein all grain boundaries within the transition metal selenide are twin boundaries with a rotation angle of 60°. These twin boundaries consist of four-membered and eight-membered rings, and the density of the twin boundaries is 10-1. 4 -10 10 cm -2 The transition metal is molybdenum or tungsten.

2. The water electrolysis hydrogen production catalyst according to claim 1, characterized in that, The content of octagonal rings in the twin boundaries is 33-60%.

3. The water electrolysis hydrogen production catalyst according to claim 1, characterized in that, The four-membered and eight-membered rings in the twin boundary are arranged at irregular or regular intervals.

4. A method for preparing a water electrolysis hydrogen production catalyst, used to prepare the water electrolysis hydrogen production catalyst according to claims 1-3, characterized in that, The preparation method includes: (1) Dissolve the transition metal salt and strong base in water to obtain a precursor solution; (2) Spin-coating the precursor solution onto the substrate; (3) Place the substrate in the middle of the tubular furnace, place the selenium powder at the gas inlet end of the tubular furnace, evacuate the tubular furnace and fill it with reducing gas and inert gas, heat it to sublimate the selenium powder, and make it react with the precursor solution and anneal it. (4) Spin-coat the PMMA solution onto the surface of the transition metal selenide, dry it and then put it into the NaOH aqueous solution. After the transition metal selenide is detached from the surface of the growth substrate, pick it up with a substrate with electrodes, dry it, and wash off the PMMA on the surface of the transition metal selenide. Finally, transfer the transition metal selenide from the growth substrate to the substrate.

5. The preparation method according to claim 4, characterized in that, The preparation method further includes step (5): covering the entire device with a PMMA film, and then removing the PMMA above the region of interest in the transition metal selenide nanosheet with EBL, with the exposed portion of the transition metal selenide serving as a catalyst.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the transition metal salt to the strong base is 1-10:

2.

7. The preparation method according to claim 4, characterized in that, The substrate is a sapphire substrate or a SiO2 / Si substrate.

8. The preparation method according to claim 4, characterized in that, In step (3), the heating includes: the middle part of the tubular furnace is heated to 700-800℃ at a rate of 40-50℃ / min and then held for 1-10 minutes; the gas inlet end of the tubular furnace is heated to 300-350℃ at a rate of 40-50℃ / min and then held for 1-10 minutes.

9. The application of the water electrolysis hydrogen production catalyst according to any one of claims 1-3 or the water electrolysis hydrogen production catalyst obtained by the preparation method according to any one of claims 4-8 in water electrolysis hydrogen production.

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