Process and Application of Low-Temperature Preparation of Few-Layer Molybdenum Diselenide Nanofilm

Abstract

The present invention discloses a process and application for preparing molybdenum diselenide nanofilms at low temperature. By constructing a precise selenium-molybdenum source concentration regulation system and combining with the structural optimization design of the molybdenum source precursor, the preparation of few-layer molybdenum diselenide nanofilms with controllable layer number and high crystallization quality is realized. Specifically, first, the molybdenum foil is heated to a certain temperature in a tube furnace, and then deionized water is introduced to synthesize molybdenum oxide foil in a water vapor microenvironment. Then, using the obtained molybdenum oxide foil and selenium powder as precursors, by regulating the gradient field of the selenium powder sublimation temperature and the substrate temperature and the selenium-molybdenum source concentration, a large-area few-layer molybdenum diselenide nanofilm is obtained. The experimental results show that this method has the advantages of low growth temperature, high synthesis efficiency, and controllable layer number. In the electrocatalytic hydrogen evolution test, the few-layer molybdenum diselenide exhibits significantly better performance than the single-layer structure. The present invention provides a new strategy for the large-scale preparation of two-dimensional transition metal chalcogenides and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of chalcogenide thin films and optoelectronic detector preparation, and particularly relates to the process and application of preparing few-layer molybdenum diselenide nanofilms at low temperature. Background Art

[0002] Transition metal chalcogenides (TMDs), as an important class of two-dimensional materials, are represented as the MX2 type, where M is a transition metal element (such as tungsten, molybdenum, etc.), and X is a chalcogen element (such as selenium, tellurium, sulfur, etc.). Due to their adjustable bandgap, high specific surface area, high carrier mobility, high on / off ratio, and unique photo / electrocatalytic activity and other characteristics, these compounds show broad application potential in the fields of optoelectronics, electricity, catalysis, and energy conversion. Among many TMDs, molybdenum diselenide (MoSe2) has attracted much attention due to its narrow bandgap (about 1.5 eV, lower than 1.9 eV of molybdenum disulfide), high density of active sites, narrow linewidth, and excellent optoelectronic properties. Especially in the field of electrochemical catalytic hydrogen evolution, the grain boundaries of few-layer MoSe2 nanofilm are rich in a large number of active sites, significantly improving its catalytic performance and enabling it to show excellent performance in the electrochemical hydrogen evolution reaction.

[0003] Currently, researchers are exploring precise preparation methods for few-layer molybdenum diselenide nanofilm. Existing synthesis techniques mainly include hydrothermal method, mechanical exfoliation, and high-temperature selenization treatment (first spin-coating the molybdenum source precursor mechanically), etc. Although certain progress has been made in these methods, there are still limitations. For example, both the hydrothermal method and mechanical exfoliation perform poorly in layer number control and sample uniformity, and it is difficult to meet the requirements of industrial production. The high-temperature selenization method has a growth temperature usually higher than 700 °C, resulting in a complex process and small grain size, which limits its application in a wider range of fields.

[0004] Therefore, it is of extremely important significance to explore a preparation method for few-layer molybdenum diselenide nanofilm that can achieve large-area preparation, simple process, low cost, and low synthesis temperature. In addition, a highly uniform nanofilm structure is crucial for achieving stable electrochemical performance, which will significantly improve the efficiency and stability of energy conversion technologies such as electrocatalytic hydrogen evolution. By optimizing the preparation process, precise control of the number of layers of molybdenum diselenide nanofilm can be achieved, thereby optimizing its physical and chemical properties. This innovative preparation method not only helps to promote the application of molybdenum diselenide nanofilm in the industrial field but also provides strong support for the development of related technologies. Summary of the Invention

[0005] In view of the problems existing in the preparation of few-layer MoSe2 nanofilms by methods such as mechanical exfoliation method, high-temperature selenization method, and hydrothermal method in the above-mentioned existing processes, such as the complication of the process flow, the difficulty of layered regulation, the limitation of grain growth, and the too high growth temperature, the present invention provides a process and application for preparing few-layer molybdenum diselenide nanofilms at low temperature. Based on the principle of chemical vapor deposition (CVD) technology, through the synergistic effect of precursor molecular structure optimization and spatial confinement growth control strategy, precise control of the number of layers of two-dimensional molybdenum diselenide nanofilms, large-area continuous growth and uniform film formation are achieved under mild conditions, not only achieving high uniformity, but also significantly reducing the growth temperature. Experimental results show that this process has the advantages of simplicity in operation, process stability, and cost-effectiveness, significantly improving the controllability and repeatability of material synthesis. In particular, the prepared two-dimensional MoSe2 film exhibits excellent performance in fields such as photodetectors, gas sensing elements, and electrocatalytic hydrogen evolution reactions, verifying its broad application prospects.

[0006] The technical solution adopted by the present invention to achieve the above object is as follows:

[0007] A process for preparing few-layer molybdenum diselenide nanofilms at low temperature, comprising the following steps:

[0008] S1. Push the metal molybdenum foil to the center of the hot zone of the tube furnace. After the temperature is programmed to rise to the range of 465 - 500 °C, translate the quartz boat loaded with deionized water to a position 4 - 5 cm away from the molybdenum foil, and carry out an oxidation reaction in an air atmosphere for 8 - 15 min to obtain a water-assisted synthesized molybdenum oxide foil.

[0009] S2. Transfer the water-assisted synthesized molybdenum oxide foil to directly above the growth substrate, and push it back to the center of the hot zone of the tube furnace. Place a quartz boat loaded with selenium powder upstream of the tube furnace according to the direction of carrier gas flow.

[0010] S3. Purge the reaction chamber with argon for cleaning. Under a mixed atmosphere of H2 / Ar, program the temperature to rise to 450 - 800 °C at the center of the hot zone of the tube furnace, and maintain it for 8 - 20 min for growth.

[0011] S4. After terminating the heating, keep the mixed gas flowing continuously. Wait for the tube furnace to cool naturally to room temperature (20 - 25 °C), and then open the tube furnace to obtain few-layer molybdenum diselenide nanofilms.

[0012] Preferably, in step S1, a molybdenum foil with a purity of 4N (99.99%) is used, and its thickness is controlled within the range of 2 to 5 μm; by loading deionized water into a quartz boat and positioning it at a distance of 4 to 5 cm from the molybdenum foil, a small amount is sufficient to construct a local water vapor microenvironment. The inventor unexpectedly found during the experiment that this design can promote the amorphous transformation of molybdenum oxide during the oxidation reaction stage in an air atmosphere (8 - 15 min, 465 - 500 °C), thereby significantly reducing the crystallinity of the formed molybdenum oxide foil. This structural characteristic significantly promotes the layer-limited growth mechanism of the subsequent MoSe2 nanostructure, making the generated MoSe2 nanofilms mainly appear in the form of few layers.

[0013] Preferably, in step S2, the selenium powder is selenium powder with a purity of 4N (Se, 99.99%), and its dosage range is controlled within the interval of 50 - 300 mg. In the chemical vapor deposition process, the loading amount of this high-purity selenium source directly affects the saturated vapor pressure of gaseous Se species, thereby regulating the layered growth kinetics of two-dimensional MoSe2.

[0014] Preferably, in step S2, the growth substrate is soda-lime glass (SiO2 - CaO - Na2O), silicon (Si), or sapphire (α - Al2O3). Experiments have confirmed that the surface and interface characteristics of the substrate are one of the decisive factors for the growth of the two-dimensional MoSe2 layered structure, which is crucial for controlling the growth of the MoSe2 nanofilm in the form of few layers. Through the lattice matching and surface energy regulation mechanism, the preferred substrate can effectively inhibit the three-dimensional island growth mode and realize the synthesis of two-dimensional materials with a thickness-controllable few-layer configuration.

[0015] Preferably, in step S2, the confinement height between the water-assisted synthesized molybdenum oxide foil and the growth substrate is 1 to 5 mm. The design of this confinement height can effectively regulate the precursor vapor concentration gradient, inhibit the three-dimensional island growth mode, and at the same time promote the two-dimensional layer-by-layer assembly process dominated by the interlayer van der Waals force.

[0016] Preferably, in step S2, the upstream of the tube furnace is at a position 21 to 24 cm from the center of the hot zone of the tube furnace. The optimized configuration of this parameter can ensure the directional transmission of the precursor vapor under the action of the carrier gas (H2 / Ar), while avoiding the out-of-control nucleation phenomenon caused by premature thermal decomposition. Experimental verification shows that the design of the 21 - 24 cm axial spacing can maintain the selenium vapor partial pressure within the optimal process window of 0.1 - 0.5 Torr, effectively balancing the surface diffusion and chemical adsorption kinetic processes.

[0017] Preferably, in step S3, when purging the reaction chamber, the argon flow rate used for purging is set at 300 - 500 sccm, and the purging duration is 30 - 60 minutes. When performing the reaction chamber cleaning operation, it is of great significance to appropriately increase the argon flow rate. Its advantage lies in that it can fully improve the cleaning efficiency, thereby achieving a comprehensive and detailed cleaning effect, ensuring the thorough completion of the cleaning work, and meeting the process requirements.

[0018] Preferably, in step S3, the duration of the programmed temperature rise control is 25 - 35 min.

[0019] Preferably, in step S3, in the H2 / Ar mixed atmosphere, the H2 flow rate is 3 - 7 sccm, and the Ar flow rate is 65 - 150 sccm. Experimental verification shows that precisely controlling the hydrogen ratio can optimize the crystal growth kinetic process. At the same time, the reasonable regulation of the argon flow rate has multiple technical advantages. It can not only maintain the chemical inertness of the reaction system by establishing a stable hydrodynamic boundary layer, but also avoid the plasma volume polarization effect caused by too large a flow rate gradient, while achieving the economical utilization of gas resources.

[0020] The few-layer MoSe2 nanofilms obtained by the above process are applied to fields such as gas sensing elements, optoelectronic detectors, or electrocatalytic hydrogen evolution reactions, etc., and can exhibit excellent performance, with broad application prospects.

[0021] Compared with the existing process, the beneficial effects of the present technical solution are as follows:

[0022] Through an innovative precursor preparation scheme, the present invention introduces a deionized water medium in the molybdenum foil oxidation stage, achieving a significant regulation of the orderliness of the molybdenum oxide foil crystal structure (the XRD pattern shows that the grain size is reduced by about 40%). This treatment method successfully induces the formation of a layered MoO(OH)2 dielectric phase, constructing a nucleation kinetic environment suitable for the growth of few-layer MoSe2 nanofilms, thereby creating favorable conditions for the controllable preparation of large-area few-layer MoSe2 nanofilms at low temperature, making the preparation process more efficient and controllable.

[0023] (2) The present invention adopts an autocatalytic conversion mechanism, and no external catalyst is required throughout the process. It can eliminate the metal residue problem caused by the traditional catalytic system while ensuring the reaction activity, simplifies the process flow, and significantly saves the production cost.

[0024] (3) The present invention adopts atmospheric pressure chemical vapor deposition (CVD) technology. Compared with methods such as hydrothermal method, mechanical exfoliation method, and high-temperature seleniumization process after pre-coating molybdenum source, the present invention can synthesize large-area continuous, controllable-layered, and highly uniform molybdenum diselenide nanofilms, and through precise feedback control of the selenium / molybdenum molar ratio, achieve precise regulation of the number of layers of molybdenum diselenide nanofilms. Description of the Drawings

[0025] Figure 1 Digital photos of molybdenum oxide foils synthesized by anhydrous-assisted synthesis and water-assisted synthesis in Example 1;

[0026] Figure 2 Raman spectroscopy characterization diagrams of molybdenum oxide foils synthesized by anhydrous-assisted synthesis and water-assisted synthesis in Example 1;

[0027] Figure 3 Raman spectroscopy characterization diagram of molybdenum oxide foil synthesized by water-assisted synthesis in Example 1;

[0028] Figure 4 X-ray diffraction characterization diagram of molybdenum oxide foil synthesized by water-assisted synthesis in Example 1;

[0029] Figure 5 X-ray diffraction characterization diagram of molybdenum oxide foil synthesized by anhydrous-assisted synthesis in Example 1;

[0030] Figure 6 Optical microscope characterization diagram of molybdenum diselenide obtained in Example 2;

[0031] Figure 7 Characterization diagram of the Raman spectrum of molybdenum diselenide obtained in Example 2;

[0032] Figure 8 Optical microscope characterization diagram of molybdenum diselenide obtained in Example 3;

[0033] Figure 9 Scanning electron microscope characterization diagram of molybdenum diselenide obtained in Example 3;

[0034] Figure 10 Atomic force microscope characterization diagram of molybdenum diselenide obtained in Example 3;

[0035] Figure 11 Characterization diagram of the Raman spectrum of molybdenum diselenide obtained in Example 3;

[0036] Figure 12 Characterization diagram of the photoluminescence of molybdenum diselenide obtained in Example 3;

[0037] Figure 13 X-ray energy spectrum characterization diagrams of the Mo 3d orbit and Se 3d orbit of molybdenum diselenide obtained in Example 3;

[0038] Figure 14 Low-magnification transmission electron microscope (a) and high-magnification transmission electron microscope characterization diagrams (b) of molybdenum diselenide obtained in Example 3;

[0039] Figure 15 Optical microscope characterization diagram of a large-area single-layer molybdenum diselenide nanofilms (selenium powder mass is 100 mg) obtained in Example 4;

[0040] Figure 16 Optical microscope characterization diagram of the large-area single / double mixed-layer molybdenum diselenide nanofilms obtained in Example 4 (mass of selenium powder is 150 mg);

[0041] Figure 17 Optical microscope characterization diagram of the large-area double-layer molybdenum diselenide nanofilms obtained in Example 4 (mass of selenium powder is 200 mg);

[0042] Figure 18 Optical microscope characterization diagram of the large-area few-layer molybdenum diselenide nanofilms obtained in Example 4 (mass of selenium powder is 250 mg);

[0043] Figure 19 Optical microscope characterization diagram of the large-area single-layer molybdenum diselenide nanofilms obtained in Example 4 (oxidation temperature of molybdenum foil is 465 °C);

[0044] Figure 20 Optical microscope characterization diagram of the large-area single / double mixed-layer molybdenum diselenide nanofilms obtained in Example 4 (oxidation temperature of molybdenum foil is 475 °C);

[0045] Figure 21 Optical microscope characterization diagram of the large-area double-layer molybdenum diselenide nanofilms obtained in Example 4 (oxidation temperature of molybdenum foil is 485 °C);

[0046] Figure 22 Optical microscope characterization diagram of the large-area few-layer molybdenum diselenide nanofilms obtained in Example 4 (oxidation temperature of molybdenum foil is 495 °C);

[0047] Figure 23 Optical microscope characterization diagram of the single-layer molybdenum diselenide nanosheets obtained in Example 5;

[0048] Figure 24 Atomic force microscope characterization diagram of the single-layer molybdenum diselenide nanosheets obtained in Example 5;

[0049] Figure 25 Electrochemical performance test results of the single-layer molybdenum diselenide nanosheets and large-area few-layer molybdenum diselenide nanofilms in Example 6. Detailed implementation manners

[0050] The technical solutions of the present invention will be elaborated in detail below in conjunction with the accompanying drawings and specific embodiments. However, it should be noted that the protection scope of the present invention is not limited to the following embodiments. Example 1

[0051] Place the molybdenum foil in the center of the hot zone of a tube furnace. Heat it up to 475 °C at a rate of 19 °C / min using the programmed temperature rise method. Subsequently, push a quartz boat containing 1.5 ml of deionized water to a position 5 cm away from the molybdenum foil, and conduct oxidation treatment in an air atmosphere. After 10 min, turn off the heat source and wait for the furnace body to cool naturally to room temperature to obtain a water-assisted synthesized molybdenum oxide foil.

[0052] Through macroscopic morphology comparative analysis (as Figure 1 shown), there are significant differences between the anhydrous-assisted synthesized and water-assisted synthesized molybdenum oxide foils. Raman spectroscopy tests (as Figures 2 to 3 ) show that the water-assisted synthesized molybdenum oxide foil exhibits an obvious characteristic peak at 889.8 cm -1 . This peak corresponds to the formation characteristics of the MoO(OH)2 phase, indicating that under high-temperature oxidation, the molybdenum foil reacts with water molecules to generate MoO(OH)2. Compared with the anhydrous-assisted synthesized molybdenum oxide foil, the intensity of the Raman characteristic peak of the water-assisted synthesized molybdenum oxide foil is significantly weakened, and the main peak undergoes a slight low-frequency shift. In addition, the full width at half maximum (FWHM) of the Raman characteristic peak of the water-assisted synthesized molybdenum oxide foil becomes wider, indicating a significant increase in the lattice defect density.

[0053] To deeply reveal the influence of deionized water treatment on the structure of the molybdenum oxide foil, X-ray diffraction (XRD) technology was used for phase analysis (as Figures 4 to 5 ). The results show that the diffraction peak intensity of the water-assisted synthesized molybdenum oxide foil at 31.7° (corresponding to the (110) crystal plane of MoO3) is significantly lower than that of the anhydrous-assisted synthesized molybdenum oxide foil, confirming a significant reduction in its crystal order. In addition, the present invention also found a relatively obvious diffraction peak of MoO(OH)2, once again proving that the hydrothermal process successfully induced the formation of molybdenum oxyhydroxide intermediate (MoO(OH)2). Example 2

[0054] Substrate pretreatment:

[0055] Select a soda-lime glass substrate with a thickness of 1.0 mm (size 0.7 cm × 2 cm) and place it on the surface of a graphite sheet. Cut the water-assisted synthesized molybdenum oxide foil into a rectangular piece with a specification of 2 cm × 1.5 cm, fold it in half along the width direction to form a microstructure with an edge height of 2.0 ± 0.1 mm, so that the confined height between the molybdenum oxide foil and the glass substrate is 1.0 mm.

[0056] Film deposition system assembly:

[0057] Push the molybdenum oxide foil and the glass substrate together into the center of the hot zone of the tube furnace. Load 275 mg of selenium powder into the quartz boat and place it in the upstream area 18.5 cm away from the center of the hot zone in the gas flow direction. After sealing the cavity, perform pretreatment: introduce argon at a flow rate of 512 sccm to displace the reaction chamber for 5 min, and then switch to a hydrogen-argon mixture (H2: 6 sccm, Ar: 65 sccm) and continue to purge for 2 min to make the gas environment in the tube furnace tend to be stable.

[0058] Chemical vapor deposition process:

[0059] Adopt a two-stage heating program: in the initial stage, heat up to 450 °C at a rate of 15 °C / min (taking 25 min), and maintain this temperature for a growth reaction of 12 min. After the reaction ends, cool naturally to room temperature to obtain the target product, and take out the soda-lime glass substrate grown with molybdenum diselenide for analysis.

[0060] Observed by optical microscope (OM) ( Figure 6 ), it can be seen that the MoSe2 thin film prepared by using the water-assisted synthesized molybdenum oxide foil presents a typical few-layer nanostructure with uniform lateral size distribution. Figure 7 The Raman spectrum also indicates the successful construction of a few-layer structure with a low defect density. Example 3

[0061] On the basis of maintaining the substrate treatment process of Example 1, adjust the heat treatment parameters: heat the heating zone of the tube furnace to 750 °C in a 25-min program, and adjust the loading position of the quartz boat to the upstream area 22.5 cm away from the heating center. The remaining process parameters (gas flow rate, pretreatment time, etc.) are maintained as set in Example 1. After the reaction ends, cool naturally to room temperature to obtain the target product. The morphology of the molybdenum diselenide thin film prepared in Example 3 is as Figure 8 shown. It can be seen from Figure 8 that the molybdenum diselenide thin film grown with the water-assisted synthesized molybdenum oxide foil as the precursor presents a typical few-layer nanostructure.

[0062] Figure 9 The scanning electron microscope (SEM) shows that the thin film is distributed in a uniform island shape; Figure 10 The atomic force microscope (AFM) reveals monolayer and bilayer structures, and there are significant surface topography undulations (obvious wrinkles) in the bilayer region. From Figure 11 the Raman spectrum characterization diagram, it can be seen that, compared with the literature data, the positions of the A 1g characteristic peaks in the monolayer, bilayer and trilayer structures have all undergone red shifts. This phenomenon is mainly due to the existence of a certain number of selenium vacancies inside the sample, and during the cooling process, strain is generated due to the thermal mismatch between the material and the substrate. E 2g 1The peak is consistent with the literature data, further confirming that the grown sample is a few-layer MoSe2 nanothin film structure.

[0063] From Figure 12 the photoluminescence characterization diagram, it can be observed that due to the direct bandgap characteristic of monolayer MoSe2 nanothin film, a significant characteristic peak appears at 808 nm. In contrast, for bilayer and trilayer MoSe2 nanothin films, due to their indirect bandgaps, photon transitions are quenched, so the intensity of the characteristic peak is lower.

[0064] Figure 13 The X-ray energy spectrum characterization diagram of 5 / 2 further determines the chemical composition of the few-layer MoSe2 nanothin film structure. In the Mo3d diagram, two characteristic peaks can be observed, corresponding to Mo 3d 3 / 2 and Mo 3d 5 / 2 and Se3d 3 / 2 respectively, with binding energies of 228.53 eV and 231.58 eV. Similarly, in the Se 3d spectrum diagram, two characteristic peaks are also observed, corresponding to Se 3d

[0065] Figure 14 shows the transmission electron microscope (TEM) characterization results of few-layer molybdenum diselenide nanothin films. From Figure 14 a, it can be observed that the few-layer molybdenum diselenide nanothin film exhibits a typical layered structure, and its edge part shows obvious atomic layer stacking characteristics. This layered structure is a typical feature of molybdenum diselenide, indicating that the sample has a good crystal structure and few layers.

[0066] In Figure 14 b, the high-resolution transmission electron microscope image further reveals the atomic arrangement of the few-layer molybdenum diselenide nanothin film. It can be seen that the atomic arrangement presents a highly ordered hexagonal lattice structure, which is consistent with the crystal structure of molybdenum diselenide. The spacing between each atomic layer is about 0.615 nm, which is consistent with the theoretical layer spacing of molybdenum diselenide, further confirming the high quality and few-layer characteristics of the sample.

[0067] In addition, no obvious defects or impurities are observed in the transmission electron microscope image, indicating that the prepared few-layer molybdenum diselenide nanothin film has high purity and crystallinity. Such high-quality few-layer molybdenum diselenide nanothin films have important application prospects in optoelectronic devices and the catalytic field. Example 4

[0068] Based on the growth process of Example 2, by adjusting the concentration of selenium and the oxidation temperature of molybdenum foil (using the water-assisted method), the control of the number of layers of molybdenum diselenide nanofilms was successfully achieved, while other experimental conditions remained unchanged. The characterization results are as Figure 15 shown in Figures 2 to 22. The research results show that the number of layers of molybdenum diselenide changes with the concentration of selenium powder and the oxidation temperature of molybdenum foil. When the selenium concentration and the oxidation temperature of molybdenum foil are low, the molybdenum diselenide samples are mainly monolayer nanofilms. With the increase of the selenium powder concentration and the oxidation temperature of molybdenum foil, the samples gradually change from monolayer to bilayer, and finally, when the selenium powder concentration and the oxidation temperature of molybdenum foil are too high, molybdenum diselenide is mainly composed of three layers and few layers. In addition, the research of the present invention also found that more bilayer and trilayer molybdenum diselenide nucleate at grain boundaries and grow inward. This is mainly attributed to the fact that during the growth process, the defects at grain boundaries make the energy required for molybdenum diselenide to nucleate at grain boundaries lower, thus making it easier to induce the growth of molybdenum diselenide at grain boundaries. Example 5

[0069] Based on the growth process of Example 3, with other experimental conditions unchanged, when using anhydrous-assisted synthesized molybdenum oxide foil as the precursor, the grown molybdenum diselenide is mainly monolayer nanosheets, and its optical microscope characterization is as Figure 23 shown. In addition, Figure 24 the atomic force microscope characterization results also further confirm the successful preparation of monolayer molybdenum diselenide nanosheets. Example 6

[0070] Electrochemical hydrogen evolution performance tests were carried out on monolayer MoSe2 nanosheets and few-layer MoSe2 nanofilms. As Figure 25 shown, in a saturated KCl solution, an electrochemical hydrogen evolution reaction was carried out using AgCl as the reference electrode. It can be seen from the linear sweep voltammetry (LSV) curve in Figure a that when the current is 10 mA / Cm 2 , the few-layer MoSe2 nanofilm has a lower initial potential compared to the monolayer MoSe2 nanosheet. Figures b and c respectively show the Tafel slope and impedance of few-layer MoSe2 and monolayer MoSe2. The few-layer MoSe2 nanofilm shows a lower Tafel slope and impedance compared to the monolayer MoSe2 nanosheet, indicating that the few-layer MoSe2 nanofilm has better catalytic performance. Figure d is the linear sweep voltammetry curve of the few-layer MoSe2 nanofilm after 5000 cycles. It can be seen from the figure that the sample still has excellent catalytic performance after 5000 cycles, and the initial potential does not increase significantly at a current of 10 mA / Cm 2 , indicating that the sample has high stability.

Claims

1. A process for preparing a few-layer MoSe nanofilm at low temperature, characterized in that: The steps include: S1. Push the metal molybdenum foil to the center of the hot zone of the tube furnace, raise the temperature to 465 ~ 500 ℃, move the quartz boat loaded with deionized water to a position 4 ~ 5 cm away from the molybdenum foil, and perform an oxidation reaction in an air atmosphere for 8 ~ 15 min to obtain water-assisted synthesized oxidized molybdenum foil; S2. The molybdenum oxide foil prepared by water-assisted synthesis is transferred to the top of the growth substrate, the confinement height between the molybdenum oxide foil prepared by water-assisted synthesis and the growth substrate is 1 to 5 mm, and it is pushed back to the center of the hot zone of the tube furnace. A quartz boat loaded with selenium powder is placed upstream of the tube furnace according to the flow direction of the carrier gas. The upstream of the tube furnace is 21 to 24 cm away from the center of the hot zone of the tube furnace. S3. The reaction chamber is purged with argon gas for cleaning. In a H2 / Ar mixed atmosphere, the temperature in the center of the hot zone of the tube furnace is raised to 450-800°C by program temperature increase and maintained for 8-20 min for growth. S4. After terminating the heating, the mixed gas is kept flowing, and the tube furnace is naturally cooled to 20-25° C., and then the tube furnace is opened to obtain a few-layer molybdenum diselenide nanofilm.

2. The process for preparing a few-layer MoSe2 nanofilm at low temperature according to claim 1, characterized in that: In step S1, a metal molybdenum foil with a purity of 4N grade is used, and its thickness is controlled to be 2 to 5 μm.

3. The process for preparing a few-layer MoSe nanofilm at low temperature according to claim 1, characterized in that: In step S2, the selenium powder is 4N grade purity selenium powder, and its usage range is controlled in the range of 50-300 mg.

4. The process for preparing a few-layer MoSe2 nanofilm at low temperature according to claim 1, characterized in that: In step S2, the growth substrate is one of soda-lime glass, sapphire or silicon.

5. The process for preparing a few-layer MoSe2 nanofilm at low temperature according to claim 1, characterized in that: In step S3, the argon gas flow rate used for purging is set at 300-500 sccm, and the purging time is 30-60 minutes.

6. The process for preparing a few-layer MoSe2 nanofilm at low temperature according to claim 1, characterized in that: In step S3, the programmed temperature control time is 25 to 35 minutes.

7. The process for preparing a few-layer MoSe2 nanofilm at low temperature according to claim 1, characterized in that: In step S3, in the H2 / Ar mixed atmosphere, the H2 flow rate is 3 to 7 sccm, and the Ar flow rate is 65 to 150 sccm.

8. Use of the few-layer MoSe2 nanofilm obtained by the process according to any one of claims 1 to 7 in gas sensor elements, photoelectron detectors or electrocatalytic hydrogen evolution reactions.

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