SnS2 / MoS2-based pec type photodetector and preparation method of snS2 / moS2 heterojunction

Abstract

The application relates to the field of photoelectric detection, in particular to a PEC type photoelectric detector based on SnS2 / MoS2 and a preparation method of the SnS2 / MoS2 heterojunction. The PEC type photoelectric detector based on SnS2 / MoS2 comprises an electrolyte tank, a reference electrode, a working electrode and a counter electrode, the fixed ends of the reference electrode, the working electrode and the counter electrode are fixed on the cover of the electrolyte tank through clamping holes, the free ends are suspended in the electrolyte tank and do not contact the bottom of the electrolyte tank, the working electrode comprises a conductive base, a MoS2 layer and a SnS2 layer, the MoS2 layer is in contact with the conductive base, and the SnS2 layer is arranged on the side of the MoS2 layer away from the conductive base, namely the working substance of the working electrode is the SnS2 / MoS2 heterojunction. The preparation steps of the SnS2 / MoS2 heterojunction are as follows: S1, using a chemical vapor deposition method to prepare MoS2 nanosheets on the conductive base; S2, using the conductive base with the MoS2 nanosheets grown in step S1 as a deposition base to grow SnS2 nanosheets.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photoelectric detection, in particular to a PEC type photoelectric detector based on SnS2 / MoS2 and a preparation method of SnS2 / MoS2 heterojunction. BACKGROUND

[0002] A photoelectric detector is a photoelectric device prepared based on the principle of photoelectric effect of semiconductor materials. In recent years, photoelectrochemical (PEC) type detectors as a new type of photoelectric detection have attracted much attention. Compared with field effect tube photoelectric detectors, two-dimensional material based PEC type detectors have closer contact with electrolyte, shorter electron transport path (nm level), low cost, are conducive to popularization, and can work for a long time without external bias. In addition, PEC type detectors based on good photoelectrode materials can also be applied to PEC water hydrolysis. These advantages make it have good application prospect.

[0003] However, the photoelectric detector in the prior art has the problems of insufficient accuracy and sensitivity and poor environmental stability due to the complex structure and single photoelectrode material of the photoelectric detector, so that it is difficult to be applied on a large scale in the field of photoelectric detection. SUMMARY

[0004] The present application aims at the deficiencies in the prior art, and provides a PEC type photoelectric detector based on SnS2 / MoS2 and a preparation method of SnS2 / MoS2 heterojunction, so as to solve the problems of insufficient accuracy and sensitivity and poor environmental stability in the prior art.

[0005] The technical concept of the present application is as follows: the existing photoelectric detector photoelectric detection accuracy and sensitivity is poor mainly due to the slow separation and transport process of photo-generated carriers in photoelectric detection, which is mainly caused by two reasons, one is that the working substance on the working electrode is not suitable, and the other is that the working substance on the working electrode and the conductive substrate of the working electrode are not close enough and easy to fall off. The working substance of the present application is SnS2 / MoS2 heterojunction, and MoS2 nanosheet is laid on the conductive substrate, and SnS2 nanosheet is grown vertically on MoS2 nanosheet, so that the specific surface area of SnS2 / MoS2 heterojunction is larger, which can produce more photo-generated carriers, and the built-in electric field formed in the heterojunction accelerates the separation and transport process of photo-generated carriers; the present application adopts chemical vapor deposition method to prepare SnS2 / MoS2 heterojunction, and the substrate in the growth process is the conductive substrate of the working electrode, since the chemical vapor deposition method can realize the growth of atomic level nanomaterials, so the contact between the working substance prepared by this method and the conductive substrate of the working electrode is very close, so that the contact resistance is very small, which accelerates the transport process of photo-generated carriers, therefore the detection accuracy and sensitivity of the photoelectric detector of the present application is higher.

[0006] In order to realize the above technical concept, in order to solve the technical problem of "insufficient accuracy and sensitivity and poor environmental stability" of the existing photoelectric detector, the technical scheme adopted by the present application is as follows:

[0007] The application provides a SnS2 / MoS2-based PEC type photoelectric detector. The photoelectric detector comprises an electrolyte tank, a reference electrode, a working electrode and a counter electrode. The fixed ends of the reference electrode, the working electrode and the counter electrode are fixed on the cover of the electrolyte tank through the clamping holes, and the free ends of the reference electrode, the working electrode and the counter electrode are suspended in the electrolyte tank, and the distance from the bottom of the electrolyte tank is about 3-5 cm, so that the reference electrode, the working electrode and the counter electrode are not in contact with the bottom of the electrolyte tank, and the photoelectrochemical reaction is more sufficient. The corresponding position of the electrolyte tank and the working electrode is a light-transmitting material. The material of the reference electrode is mercury-mercurous sulfate, the material of the counter electrode is platinum, and the working substance of the working electrode is a SnS2 / MoS2 heterojunction. The working electrode comprises a conductive substrate, a MoS2 layer and a SnS2 layer, the MoS2 layer is in contact with the conductive substrate, and the SnS2 layer is arranged on the side of the MoS2 layer away from the conductive substrate. More specifically, the MoS2 layer is a single-layer MoS2 nanosheet, and the thickness is laid on the conductive substrate. The SnS2 layer is a SnS2 nanosheet, the SnS2 nanosheet is upright on the MoS2 nanosheet, and the upright height of the SnS2 nanosheet is 300-500 nm. The SnS2 nanosheet perpendicular to the MoS2 nanosheet has a large specific surface area, and the MoS2 nanosheet and the SnS2 nanosheet form a van der Waals heterojunction to generate a built-in electric field. On the one hand, more photo-generated carriers can be generated, and on the other hand, the separation and transport process of the generated photo-generated carriers is fast, thereby improving the photoelectric response of the photoelectric detector, so that the photoelectric detection accuracy and the sensitivity of the photoelectric detector are both high. The intensity of the photoelectric response corresponds to the improvement of the photoelectric detection accuracy, and the response time or the recovery time of the photoelectric response corresponds to the improvement of the sensitivity of the photoelectric detector. Therefore, the photoelectric detector can be applied to a high-sensitivity and high-accuracy requirement without an external bias.

[0008] The application also provides a preparation method of the SnS2 / MoS2 heterojunction. The method comprises two steps of chemical vapor deposition process. First, sulfur powder and MoO3 powder are used as precursors to grow MoS2 nanosheets on a conductive substrate, and then the conductive substrate with the grown MoS2 nanosheets is used as a new growth substrate to grow SnS2 nanosheets thereon. Specifically, sulfur powder, SnCl4·5H2O powder or sulfur powder and SnO2 powder are used as precursors for growth. The two growth processes are both grown under low pressure and in argon protection.

[0009] As a comparison, the application also prepares SnS2 / MoS2 heterojunctions with different densities of upright SnS2 nanosheets, and single MoS2 nanosheets and SnS2 nanosheets, and compares the photoelectric detection performance of the working substance of the working electrode. The results show that the detection accuracy and the sensitivity of the SnS2 / MoS2-based PEC type photoelectric detector are higher.

[0010] Compared with the prior art, the application has the following beneficial effects:

[0011] (1) Because of the existence of the built-in electric field in the SnS2 / MoS2 heterojunction, the separation and transmission process of the photo-generated carriers is faster, and the upright SnS2 nanosheet is uprightly distributed on the MoS2 nanosheet, so that the specific surface area of the SnS2 nanosheet is larger, more photo-generated carriers can be generated, and the separation and transmission process of the photo-generated carriers is faster, that is, the intensity and speed of the photoelectric response are faster, therefore, the accuracy and sensitivity of the photoelectric detection of the PEC type photoelectric detector based on SnS2 / MoS2 provided by the application are higher, so that it can be applied in an environment with high requirements for photoelectric detection accuracy and sensitivity. At the same time, the PEC type photoelectric detector based on SnS2 / MoS2 of the application does not need an external bias voltage when in use, and can be self-powered, and can complete photoelectric detection under the irradiation of incident light, so as to still be able to perform photoelectric detection in a special environment without an external power supply bias, and has good environmental adaptability and flexibility. The photoelectric detector can also be used for photoelectrochemical catalytic hydrogen production, can realize multiple purposes, and makes the catalytic hydrogen production process more convenient and clean. Compared with SnS2 nanosheets or MoS2 nanosheets as working substances, the stability of the PEC type photoelectric detector based on SnS2 / MoS2 of the application is better.

[0012] (2) The application also discloses a preparation method of the SnS2 / MoS2 heterojunction, and specifically, the SnS2 / MoS2 heterojunction is successfully prepared, in which the SnS2 nanosheet is uprightly distributed on the MoS2 nanosheet, and the contact between the MoS2 nanosheet and the conductive substrate is very close, so that the contact resistance between the MoS2 nanosheet and the conductive substrate is reduced, and the transmission process is faster, and the photoelectric response speed is faster, therefore, the accuracy and sensitivity of the photoelectric detection of the PEC type photoelectric detector based on SnS2 / MoS2 provided by the application are higher. It is also disclosed that the greater the density of the upright SnS2 nanosheet deposited on the MoS2 nanosheet, the higher the accuracy and sensitivity of the photoelectric detection. The preparation method provided by the application has the characteristics of simple process, good repeatability, low cost, safety and non-toxicity, and can prepare SnS2 / MoS2 high-quality heterojunction in a large area, thereby creating a good prerequisite for large-scale production of the PEC type self-powered photoelectric detector. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A schematic diagram of a PEC type photoelectric detector based on SnS2 / MoS2 provided by the application;

[0014] Figure 2 A schematic diagram of a working electrode in a PEC type photoelectric detector based on SnS2 / MoS2 provided by the application;

[0015] Figure 3 A schematic diagram of a preparation method of a SnS2 / MoS2 heterojunction in a PEC type photoelectric detector based on SnS2 / MoS2 provided by the present application;

[0016] Figure 4 Raman spectra of SnS2 obtained from step S33 of Example 3, MoS2 obtained from step S13 of Example 1, SnS2 / MoS2 heterojunction obtained from step S23 of Example 1, and H-SnS2 / MoS2 heterojunction obtained from step S23 of Example 2;

[0017] Figure 5 Optical images and scanning electron microscope morphology characterization images of MoS2 obtained from step S13 of Example 1 (a), H-SnS2 obtained from step S43 of Example 4 (b), SnS2 / MoS2 heterojunction obtained from step S23 of Example 1 (c), and H-SnS2 / MoS2 heterojunction obtained from step S23 of Example 2 (d); Figure 5 Figure 5 Figure 5 Figure 5 Optical images and scanning electron microscope morphology characterization images of MoS2 obtained from step S13 of Example 1 (a), H-SnS2 obtained from step S43 of Example 4 (b), SnS2 / MoS2 heterojunction obtained from step S23 of Example 1 (c), and H-SnS2 / MoS2 heterojunction obtained from step S23 of Example 2 (d);

[0018] Figure 6 Photoelectric current density curves of PEC type photoelectric detectors based on MoS2 obtained from step S13 of Example 1, SnS2 obtained from step S33 of Example 3, H-SnS2 obtained from step S43 of Example 4, SnS2 / MoS2 heterojunction obtained from step S23 of Example 1, and H-SnS2 / MoS2 heterojunction obtained from step S23 of Example 2 under different light powers at 0V bias;

[0019] Figure 7 Photoelectric current density and light response rate curves of PEC type photoelectric detectors based on MoS2 obtained from step S13 of Example 1, SnS2 obtained from step S33 of Example 3, H-SnS2 obtained from step S43 of Example 4, SnS2 / MoS2 heterojunction obtained from step S23 of Example 1, and H-SnS2 / MoS2 heterojunction obtained from step S23 of Example 2 under different light powers at 0V bias;

[0020] Figure 8 ​​​The photocurrent density curves of the PEC type photodetector based on MoS2 obtained in step S13 of Embodiment 1 of the present application, SnS2 obtained in step S33 of Embodiment 3, H-SnS2 obtained in step S43 of Embodiment 4, SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 2 under light / dark changes of the same light power at different wavelengths (350 nm, 380 nm, 420 nm, 450 nm, 475 nm, 500 nm, 520 nm, 550 nm, 600 nm, 650 nm) under 0 V bias;

[0021] Figure 9 The photocurrent density and photoresponse rate diagrams of the PEC type photodetector based on MoS2 obtained in step S13 of Embodiment 1 of the present application, SnS2 obtained in step S33 of Embodiment 3, H-SnS2 obtained in step S43 of Embodiment 4, SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 2 at different wavelengths under 0 V bias;

[0022] Figure 10 The response / recovery time diagrams and summary diagrams of the PEC type photodetector based on MoS2 obtained in step S13 of Embodiment 1 of the present application, SnS2 obtained in step S33 of Embodiment 3, H-SnS2 obtained in step S43 of Embodiment 4, SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 2 under 0 V bias;

[0023] Figure 11 The results of the photoelectrocatalytic hydrogen production of the PEC type photodetector based on MoS2 obtained in step S13 of Embodiment 1 of the present application, SnS2 obtained in step S33 of Embodiment 3, H-SnS2 obtained in step S43 of Embodiment 4, SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 2;

[0024] Figure 12 The comparison diagram of the photoelectrocatalytic / photo-catalytic / electrocatalytic hydrogen production effects of the PEC type photodetector based on H-SnS2 / MoS2 heterojunction obtained in step S23 of Embodiment 2.

[0025] Legend: 10-electrolyte tank; 20-reference electrode; 30-working electrode; 40-counter electrode; 31-conductive substrate; 32-MoS2 layer; 33-SnS2 layer. DETAILED DESCRIPTION

[0026] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0027] Example 1:

[0028] This invention provides a PEC-type photodetector based on SnS2 / MoS2, such as... Figure 1 As shown, the photodetector includes an electrolyte tank 10, a reference electrode 20, a working electrode 30, and a counter electrode 40. The fixed ends of the reference electrode 20, working electrode 30, and counter electrode 40 are fixed by clips on the cover of the electrolyte tank 10. The reference electrode 20, working electrode 30, and counter electrode 40 can be perpendicular or not perpendicular to the bottom of the electrolyte tank 10. The side of the working electrode 30 with the SnS2 / MoS2 heterojunction should be perpendicularly illuminated by the light to be measured. This allows the working electrode 30 to absorb the light to be measured to the maximum extent, thereby generating more photogenerated electrons and holes. Preferably, the reference electrode 20, working electrode 30, and counter electrode 40 are perpendicular to the bottom of the electrolyte tank 10, and the light to be measured illuminates the working electrode 30 horizontally. This improves the space utilization of the electrolyte tank 10, making the photodetector compact and portable. The other ends of the reference electrode 20, working electrode 30, and counter electrode 40 are suspended within the electrolyte tank 10 and do not contact each other. The distance between these ends and the bottom of the electrolyte tank 10 is approximately 3-5 cm. This ensures that the reference electrode 20, working electrode 30, and counter electrode 40 do not contact the bottom of the electrolyte tank 10, allowing for more sufficient light reception and ensuring adequate contact between them and the electrolyte during use. This results in a more complete photoelectrochemical reaction, generating more photogenerated carriers and improving the accuracy and sensitivity of the photodetector. The specific dimensions of the reference electrode 20, working electrode 30, and counter electrode 40 are determined according to actual needs, specifically related to the size of the electrolyte tank 10 and the intensity of the light to be measured, and are not specifically limited here.

[0029] Specifically, the electrolyte tank 10 can be made of either a transparent or opaque material and does not chemically react with the electrolyte used during operation. However, the portion of the electrolyte tank 10 corresponding to the working electrode 30 is made of a transparent material, allowing the light to be measured to directly irradiate the working electrode 30, thereby generating a larger number of photogenerated carriers. The reference electrode 20 is made of mercury-mercurous sulfate, the counter electrode 40 is made of platinum, and the working substance of the working electrode 30 is a SnS2 / MoS2 heterojunction. More specifically, the structure of the working electrode 30 is as follows: Figure 2As shown, the working electrode 30 comprises a conductive substrate 31, a MoS2 layer 32, and a SnS2 layer 33. The conductive substrate 31 is an indium-doped tin oxide transparent conductive ITO substrate or a fluorine-doped tin oxide transparent conductive FTO substrate with a thickness of 0.5-0.8 mm, a length of 85-120 mm, and a width of 85-120 mm; the MoS2 layer 32 is formed by paving MoS2 nanosheets with a thickness of 0.6-2.0 nm, more than 90% of which are single-layer MoS2, and specifically, the MoS2 layer 32 is paved on one side of the conductive substrate 31, and the conductive substrate 31 and the MoS2 layer 32 are in close contact; the SnS2 layer 33 is a SnS2 nanosheet with a vertical height of more than 300 nm, and preferably, a SnS2 nanosheet with a vertical height of 300-500 nm, which is easier to prepare, and specifically, the SnS2 nanosheet is arranged on the other side of the MoS2 layer 32 away from the conductive substrate 31, and the SnS2 nanosheet is vertically arranged on one side of the MoS2 layer 32, i.e., the plane where the SnS2 nanosheet is located is perpendicular to the plane where the MoS2 nanosheet is located, and also perpendicular to the plane surrounded by the length and width of the conductive substrate 31, and the SnS2 nanosheet is distributed on the entire MoS2 layer 32, and since the positional relationship is at the nanometer and micrometer levels, the SnS2 nanosheet and the MoS2 nanosheet are still in close contact, and the two form a SnS2 / MoS2 heterojunction. The MoS2 layer 32 has a thickness of 0.6-2.0 nm, and the SnS2 layer 33 has a thickness, i.e., the vertical height of the SnS2 nanosheet, of more than 300 nm, which can make the edge active sites of the MoS2 nanosheet and the SnS2 nanosheet more, and the specific surface area of the material larger, which is conducive to the separation and transmission of the carriers, thereby improving the accuracy and sensitivity of the photodetector. The SnS2 nanosheet perpendicular to the MoS2 nanosheet has a larger specific surface area, and the MoS2 nanosheet and the SnS2 nanosheet form a van der Waals heterojunction to generate a built-in electric field, which can generate more photo-generated carriers on one hand, and make the separation and transmission process of the generated photo-generated carriers faster on the other hand, thereby improving the photoelectric response of the photodetector of the application, and therefore, the photodetector provided by the application has high photodetection accuracy and sensitivity, wherein the improvement of the intensity of the photoelectric response corresponds to the improvement of the accuracy of the photodetector, and the improvement of the response time or recovery time of the photoelectric response corresponds to the improvement of the sensitivity of the photodetector, and therefore, the photodetector of the application can be applied in a high-sensitivity and high-accuracy environment without an external bias.

[0030] In application, the electrolyte tank 10 is filled with electrolyte. The reference electrode 20, working electrode 30, and counter electrode 40 near the electrolyte tank 10 need to be immersed in the electrolyte. Generally, the volume of the electrolyte does not exceed two-thirds of the volume of the electrolyte tank 10. Specifically, the type, concentration, and volume of the electrolyte need to be set according to the actual situation and are not specifically limited. Commonly used electrolytes include Na2SO4, Na2SO3, and KOH solution. In this embodiment, the electrolyte is a 1 mol / L Na2SO4 aqueous solution. Figure 1 As shown, the reference electrode 20, working electrode 30, and counter electrode 40 are connected to the electrochemical workstation via external leads. Specifically, the reference electrode 20, working electrode 30, and counter electrode 40 are connected to the corresponding ports of the electrochemical workstation for detecting and simultaneously recording the photocurrent intensity. It should be noted that, when used for hydrogen production, the applied bias voltage in this application is 0.8V (see attached specification). Figure 11 and Figure 12 The photoelectric detection process is performed under 0V bias, meaning no external bias is required, enabling self-powered operation. One end of the working electrode 30 immersed in the electrolyte is opposite to the light-transmitting window on the electrolyte tank 10. Specifically, the side with the SnS2 / MoS2 heterojunction is opposite the light-transmitting window, ensuring that the light to be measured fully illuminates the SnS2 / MoS2 heterojunction, generating a large number of photogenerated carriers. During detection, under the illumination of the light to be measured, photogenerated electrons and holes are generated in the SnS2 / MoS2 heterojunction on the working electrode 30. After separation, the photogenerated electrons transfer from the working electrode 30 to the counter electrode 40 via the external wire, where they reduce the H+ in the electrolyte. + Ions form hydrogen gas; simultaneously, the electrochemical workstation connected to the external conductor can monitor the photocurrent signal, thus reflecting the change in the light to be measured through changes in the photocurrent signal, achieving the purpose of photoelectric detection. The hole transfer path is the opposite, moving from the heterojunction of the working electrode 30 to its interface with the electrolyte, oxidizing the OH- in the electrolyte. -The ion generates oxygen. Generally, an external voltage promotes the separation and transfer process of the heterojunction carriers of the working electrode 30, thereby improving the performance of the photodetector. However, due to the high light absorption and high carrier separation and transfer rate of the SnS2 / MoS2 heterojunction, the light absorption rate and conversion rate are improved, so that the photodetector based on the SnS2 / MoS2 heterojunction has good detection performance even without an external bias. The light to be detected enters the inside of the electrolyte tank 10 through the light-transmitting window on the electrolyte tank 10 and directly irradiates on the SnS2 / MoS2 heterojunction of the working electrode 30. Due to the vertical arrangement of the SnS2 nanosheet and the MoS2 nanosheet, the SnS2 / MoS2 heterojunction has a large specific surface area, and there is a built-in electric field in the SnS2 / MoS2 heterojunction, so that the separation and transport of the photo-generated carriers are accelerated during detection, thereby improving the photoelectric response of the photodetector and improving the accuracy and sensitivity of the photodetector.

[0031] The preparation method of the SnS2 / MoS2 heterojunction is as follows:

[0032] The SnS2 / MoS2 heterojunction is prepared by twice chemical vapor deposition in the application. First, the MoS2 nanosheet is prepared on the conductive substrate 31, and then the upright SnS2 nanosheet is grown on the conductive substrate 31 with the grown MoS2 nanosheet as the deposition substrate. The chemical vapor deposition method belongs to an atomic-level preparation process, and the contact between the grown MoS2 nanosheet and the conductive substrate 31 and between the MoS2 nanosheet and the SnS2 nanosheet is very close, so that the contact resistance between the MoS2 nanosheet and the conductive substrate 31 is reduced, thereby making the transport speed of the photo-generated carriers faster. At the same time, the MoS2 nanosheet and the SnS2 nanosheet form the SnS2 / MoS2 heterojunction, and the built-in electric field in the heterojunction accelerates the separation and transport of the generated photo-generated carriers, thereby making the photoelectric response of the photodetector stronger and improving the accuracy and sensitivity of the photodetector.

[0033] S1, the MoS2 nanosheet is prepared on the conductive substrate 31 by using the chemical vapor deposition method;

[0034] S11, take a clean first quartz tube and fix it on the heating furnace. The first quartz tube is placed horizontally. 0.5-1.0g of sulfur powder, 3.5-5.0mg of MoO3 powder, and a clean conductive substrate 31 are sequentially added to the first quartz tube. The sulfur powder and MoO3 powder are placed in a straight line formed by the lowest point inside the first quartz tube. The conductive substrate 31 is placed horizontally inside the first quartz tube. In this embodiment, the conductive substrate 31 is specifically an indium-doped tin oxide transparent conductive ITO substrate. The length of the constant temperature heating zone of the heating furnace used in this invention is 46cm. The outer diameter of the first quartz tube matches the shape of the furnace chamber. Specifically, the outer diameter of the quartz tube used in this invention is 60mm, and the sulfur powder and MoO3 powder are placed inside a quartz boat before being placed inside the first quartz tube. The end of the first quartz tube near the sulfur powder is the gas inlet end, and the end of the first quartz tube near the conductive substrate 31 is the gas outlet end. The MoO3 powder is placed between the sulfur powder and the conductive substrate 31. Figure 3 As shown. Sulfur powder is placed in the center of the constant-temperature heating zone, 32-35 cm from the gas inlet; MoO3 powder is placed in the center of the constant-temperature heating zone; and the conductive substrate 31 is placed in the center of the constant-temperature heating zone, 9-12 cm from the gas outlet. Since chemical vapor deposition (CVD) involves heating different precursors to simultaneously reach their sublimation points, and the deposition process only occurs at specific temperatures, the temperature of the precursors is not only related to the furnace temperature but also to their location, as well as the relative positions between the precursors and between the precursors and the deposition substrate. Otherwise, the gaseous states of the precursors cannot simultaneously exist within the first quartz tube, thus preventing them from reacting. Alternatively, the unreacted material vapors cannot be effectively deposited on the deposition substrate to form nanosheets. Therefore, the temperature and distance parameters in the preparation method of this application are crucial; deviating from the relevant temperature and distance parameters will prevent the acquisition of MoS2 nanosheets.

[0035] S12, seal both ends of the first quartz tube using flanges, ensuring the gas inlet is near the sulfur powder side and the gas outlet is near the conductive substrate 31 side. Use a vacuum pump to reduce the pressure inside the first quartz tube to below 100 Pa to expel air and prevent it from affecting the reaction process during heating, such as causing oxidation. Then open the valves at both the gas inlet and outlet ends and continuously introduce gas for five minutes to further expel air from the first quartz tube. The gas flows from the sulfur powder end to the conductive substrate 31 end. Specifically, in this embodiment, the introduced gas is argon, which has stable physicochemical properties and can provide protection during the reaction. Subsequently, 20-40 sccm of argon is continuously introduced until the reaction is complete. Preferably, 30 sccm of argon is continuously introduced. The vacuum pump remains operational throughout the reaction to prevent air from entering. This deposition process can only occur at 450 Pa.

[0036] S13, set the temperature of the constant temperature heating area of the heating furnace to 680°C. Since the temperature in the first quartz tube is highest in the middle of the constant temperature heating area, i.e. 680°C, the temperature is lower closer to the two ends of the first quartz tube. The temperature of the constant temperature heating area decreases less, and the temperature decreases significantly at the edge of the constant temperature heating area. In combination with the positions and relative positions of the precursors and the conductive substrate 31 in step S11, and the sublimation temperature of MoO3 powder into a gaseous state is 680°C, the sublimation temperature of sulfur powder into a gaseous state is 200°C, and the deposition temperature of gaseous MoS2 on the conductive substrate 31 is 480-550°C, therefore, when the temperature reaches 680°C, the MoO3 powder and the sulfur powder in the first quartz tube are simultaneously gasified, and the reaction generates gaseous MoS2, which is deposited on the surface of the conductive substrate 31 downstream under the driving of argon to form MoS2 nanosheets. After natural cooling, the conductive substrate 31 on which the MoS2 nanosheets are deposited is taken out.

[0037] S2, the conductive substrate 31 on which the MoS2 nanosheets are grown obtained in step S1 is used as a deposition substrate to grow SnS2 nanosheets in a vertical shape.

[0038] S21, another clean second quartz tube is taken out, and is also fixed on the heating furnace and placed horizontally. 1.0-1.5g of sulfur powder, 0.5-1.0g of SnCl4·5H2O powder, and the conductive substrate 31 on which the MoS2 nanosheets are deposited (equivalent to the conductive substrate in step S11) are sequentially placed in the second quartz tube. Similarly, the sulfur powder and the SnCl4·5H2O powder are placed on the straight line formed at the lowest position in the second quartz tube, and the conductive substrate 31 on which the MoS2 nanosheets are deposited is placed horizontally in the second quartz tube. The sulfur powder and the SnCl4·5H2O powder are placed in the quartz boat and then placed in the second quartz tube. One end of the second quartz tube close to the sulfur powder is a gas inflow end, and the other end of the second quartz tube close to the conductive substrate 31 on which the MoS2 nanosheets are deposited is a gas outflow end. The SnCl4·5H2O powder is placed between the sulfur powder and the conductive substrate 31 on which the MoS2 nanosheets are deposited, as shown in FIG. 2. Figure 3The sulfur powder is placed in the center of the constant temperature heating area, close to the gas inlet end 32-35 cm; the SnCl4·5H2O powder is placed in the center of the constant temperature heating area; the conductive substrate 31 on which the MoS2 nanosheet is deposited is placed in the center of the constant temperature heating area, close to the gas outlet end 13-16 cm. Since the chemical vapor deposition method is to heat the different precursors to reach their own sublimation points at the same time, and the deposition process only occurs at a specific temperature, the temperature at which the precursors are located is not only related to the temperature of the heating furnace, but also related to the position at which it is located, and is closely related to the relative position between each precursor and the deposition substrate. In addition, the generated MoS2 nanosheet cannot sublimate, otherwise it will cause the gaseous state of each precursor to not exist in the second quartz tube at the same time, so as to not react with each other, or the material vapor produced by the reaction cannot be effectively deposited on the conductive substrate 31 on which the MoS2 nanosheet is deposited to generate upright SnS2 nanosheets. Therefore, the temperature and distance parameters in the preparation method of the present application are important, and the upright SnS2 nanosheet and the SnS2 / MoS2 heterojunction cannot be obtained without the related temperature and distance.

[0039] S22, the two ends of the second quartz tube are sealed using flanges, and it is necessary to note that the gas inlet end is close to the sulfur powder side, and the gas outlet end is close to the conductive substrate 31 on which the MoS2 nanosheet is deposited. The pressure in the second quartz tube is pumped to below 100 Pa using a vacuum pump, which can exhaust the air in the second quartz tube to avoid the influence of air on the reaction process when heating, such as oxidation; then open the valves at the gas inlet and outlet ends, and continuously pass the gas for five minutes to further exhaust the air in the second quartz tube. The direction of gas flow is from the sulfur powder end to the conductive substrate 31 on which the MoS2 nanosheet is deposited, which can prevent oxidation during the reaction; then continuously pass 30 sccm of argon until the reaction is completed. The vacuum pump is always kept in working condition during the reaction to prevent air from entering, and because the deposition process can only occur at low pressure.

[0040] S23, set the temperature of the constant temperature heating area of the heating furnace to 450°C. Since the temperature in the second quartz tube is highest in the middle of the constant temperature heating area, i.e. 450°C, the temperature is lower closer to the two ends of the second quartz tube, and the temperature of the constant temperature heating area decreases less, and the temperature decreases significantly at the edge of the constant temperature heating area. In combination with the positions and relative positions of the sulfur powder, SnCl4·5H2O powder, and the MoS2 nanosheet-deposited conductive substrate 31 in step S21, and the temperature at which the SnCl4·5H2O powder sublimates into a gaseous state is 450°C, the temperature at which the sulfur powder sublimates into a gaseous state is 200°C, and the temperature at which the gaseous SnS2 is deposited on the MoS2 nanosheet-deposited conductive substrate 31 is 300°C-380°C. Therefore, when the temperature reaches 450°C, the SnCl4·5H2O powder and the sulfur powder in the second quartz tube are simultaneously gasified, and the reaction generates gaseous SnS2. Under the driving of argon gas, the generated SnS2 is deposited on the surface of the MoS2 nanosheet-deposited conductive substrate 31 downstream, and the SnS2 nanosheet is deposited on the surface of the MoS2 nanosheet in a vertical shape, i.e. an SnS2 / MoS2 heterojunction is formed. After natural cooling, the conductive substrate 31 with the SnS2 / MoS2 heterojunction is taken out.

[0041] Example 2:

[0042] The difference between this embodiment and Example 1 is only that the preparation method of the SnS2 / MoS2 heterojunction is different in the following steps:

[0043] S21, take another clean second quartz tube, fix it on the heating furnace, and place it horizontally. Put 0.5-1.0g of sulfur powder, 3-4mg of SnO2 powder, and the MoS2 nanosheet-deposited conductive substrate 31 into the second quartz tube in sequence. Similarly, the sulfur powder and the SnO2 powder are placed on the straight line formed at the lowest point in the second quartz tube, and the MoS2 nanosheet-deposited conductive substrate 31 is placed horizontally in the second quartz tube. The sulfur powder and the SnO2 powder are placed in the quartz boat and then placed in the second quartz tube. The end of the second quartz tube close to the sulfur powder is the gas inflow end, and the end of the second quartz tube close to the MoS2 nanosheet-deposited conductive substrate 31 is the gas outflow end. The SnO2 powder is placed between the sulfur powder and the MoS2 nanosheet-deposited conductive substrate 31, as shown in Figure 3The sulfur powder is placed at the center of the constant temperature heating area close to the gas inflow end 12-14 cm; the SnO2 powder is placed at the center of the constant temperature heating area; and the conductive substrate 31 on which the MoS2 nanosheets are deposited is placed at the center of the constant temperature heating area close to the gas outflow end 13-15 cm. Since the chemical vapor deposition method is to make the temperatures of different precursors reach their respective sublimation points at the same time by heating, and the deposition process only occurs at a specific temperature, the temperature at the location of the precursors is not only related to the temperature of the heating furnace, but also related to the location thereof, and is closely related to the relative positions between the precursors and between the precursors and the deposition substrate. In addition, it is required that the MoS2 nanosheets that have been generated do not sublimate, otherwise the gaseous states of the precursors cannot exist in the second quartz tube at the same time, thus the reactions between the precursors cannot occur, or the material vapor generated by the reactions cannot be effectively deposited on the conductive substrate 31 on which the MoS2 nanosheets are deposited to form the upright SnS2 nanosheets. Therefore, the temperature parameter and the distance parameter in the preparation method of the present application are important, and the upright SnS2 nanosheets and the SnS2 / MoS2 heterojunction cannot be obtained without the related temperature and distance.

[0044] In step S23, the temperature of the constant temperature heating area of the heating furnace is set to 650 ℃. Since the temperature in the second quartz tube is the highest in the middle of the constant temperature heating area, i.e., 650 ℃, the closer to the two ends of the second quartz tube, the lower the temperature. The temperature of the constant temperature heating area decreases less, and the temperature decreases obviously at the edge of the constant temperature heating area. In combination with the positions and relative positions of the sulfur powder, the SnO2 powder and the conductive substrate 31 on which the MoS2 nanosheets are deposited in step S21, and the sublimation temperature of the SnO2 powder into a gaseous state is 650 ℃, the sublimation temperature of the sulfur powder into a gaseous state is 200 ℃, and the deposition temperature of the gaseous SnS2 on the conductive substrate 31 on which the MoS2 nanosheets are deposited is 300-380 ℃, when the temperature reaches 650 ℃, the SnO2 powder and the sulfur powder in the second quartz tube are gasified at the same time, and the reaction generates gaseous SnS2. Under the driving of argon, the generated SnS2 is deposited on the surface of the downstream conductive substrate 31 on which the MoS2 nanosheets are deposited, and the SnS2 nanosheets are deposited on the surface of the MoS2 nanosheets in an upright state. Since the number of the upright SnS2 nanosheets prepared in the embodiment is large and the density is high, the formed SnS2 / MoS2 heterojunction is called H(high denisity)-SnS2 / MoS2 heterojunction. After natural cooling, it can be taken out.

[0045] Example 3:

[0046] For convenience of comparison, SnS2 is grown on a conductive substrate, and the steps are as follows:

[0047] S31, take a clean third quartz tube, fix it on the heating furnace, place it horizontally, put 1.0-1.5g of sulfur powder, 0.5-1.0g of SnCl4·5H2O powder and the conductive substrate into the third quartz tube in turn, similarly, the sulfur powder and the SnCl4·5H2O powder are placed on the straight line formed at the lowest part in the third quartz tube, and the conductive substrate 31 is placed horizontally in the third quartz tube. The sulfur powder and the SnCl4·5H2O powder are placed in the quartz boat and then placed in the third quartz tube. The end of the third quartz tube close to the sulfur powder is the gas inflow end, and the end of the third quartz tube close to the conductive substrate is the gas outflow end. The SnCl4·5H2O powder is placed between the sulfur powder and the conductive substrate. The sulfur powder is placed at the center of the constant temperature heating area close to the gas inflow end 32-35cm; the SnCl4·5H2O powder is placed at the center of the constant temperature heating area; and the conductive substrate 31 is placed at the center of the constant temperature heating area close to the gas outflow end 13-16cm. Since the chemical vapor deposition method is to heat the different precursors to reach their own sublimation points at the same time, and the deposition process only occurs at a specific temperature, the temperature at the location of the precursors is not only related to the temperature of the heating furnace, but also related to the location, and also closely related to the relative position between each precursor and the deposition substrate. Otherwise, the gaseous state of each precursor cannot exist in the third quartz tube at the same time, thus cannot react with each other, or the material vapor generated by the reaction cannot be effectively deposited on the conductive substrate to form upright SnS2nanosheets. Therefore, the temperature parameters and distance parameters in the preparation method are important, and the upright SnS2nanosheets cannot be obtained without the related temperature and distance.

[0048] S32, seal the two ends of the third quartz tube using flanges, noting that the gas inflow end is close to the sulfur powder side, and the gas outflow end is close to the conductive substrate side. Use a vacuum pump to pump the pressure in the third quartz tube to below 100Pa, which can exhaust the air in the third quartz tube to avoid the influence of air on the reaction process, such as oxidation, when heating; then open the valves at the gas inflow end and the gas outflow end, and continuously pass in 200sccm of argon for five minutes, to further exhaust the air in the third quartz tube. The direction of gas flow is from the sulfur powder end to the conductive substrate end, which can prevent oxidation during the reaction process; then adjust to pass in 30sccm of argon until the reaction is completed. The vacuum pump is always kept in working condition during the reaction process to prevent air from entering, and because the deposition process can only occur at low pressure.

[0049] S33, set the temperature of the constant temperature heating area of the heating furnace to 450°C, since the temperature in the third quartz tube is highest in the middle of the constant temperature heating area, i.e. 450°C, the closer to the two ends of the third quartz tube, the lower the temperature, wherein the temperature of the constant temperature heating area decreases less, at the edge of the constant temperature heating area, the temperature decreases significantly, combined with the position and relative position of the sulfur powder, SnCl4·5H2O powder and conductive substrate in step S31, and the temperature at which the SnCl4·5H2O powder sublimates into a gaseous state is 450°C, the temperature at which the sulfur powder sublimates into a gaseous state is 200°C, and the temperature at which the gaseous SnS2 deposits on the conductive substrate is 300-380°C, therefore, when the temperature reaches 450°C, the SnCl4·5H2O powder and the sulfur powder in the third quartz tube gasify at the same time, and the reaction generates gaseous SnS2, under the driving of argon, the generated SnS2 deposits on the surface of the conductive substrate downstream, and generates the upright SnS2 nanosheet.

[0050] Example 4:

[0051] For convenience of comparison, H-SnS2 is grown on the conductive substrate, since the number of upright nanosheets obtained in this embodiment is more and the density is greater than that of the SnS2 nanosheet obtained in step S33 of Example 3, it is called H-SnS2, and the steps are as follows:

[0052] S41, take a clean fourth quartz tube, fix it on the heating furnace, place it horizontally, put 0.5-1.0g of sulfur powder, 3-4mg of SnO2 powder and a conductive substrate into the fourth quartz tube in turn, similarly, the sulfur powder and SnO2 powder are placed on the straight line formed at the lowest part in the fourth quartz tube, and the conductive substrate is placed horizontally in the fourth quartz tube. The sulfur powder and SnO2 powder are placed in the quartz boat and then placed in the fourth quartz tube. The end of the fourth quartz tube close to the sulfur powder is the gas inflow end, and the end of the fourth quartz tube close to the conductive substrate is the gas outflow end. The SnO2 powder is placed between the sulfur powder and the conductive substrate. The sulfur powder is placed at the center of the constant temperature heating area close to the gas inflow end 12-14cm; the SnO2 powder is placed at the center of the constant temperature heating area; and the conductive substrate is placed at the center of the constant temperature heating area close to the gas outflow end 13-15cm. Since the chemical vapor deposition method is to heat the different precursors to reach their own sublimation points at the same time, and the deposition process only occurs at a specific temperature, the temperature at the location of the precursors is not only related to the temperature of the heating furnace, but also related to the location, and also closely related to the relative position between each precursor and the deposition substrate. Otherwise, the gaseous state of each precursor cannot exist in the fourth quartz tube at the same time, thus cannot react with each other, or the material vapor generated by the reaction cannot be effectively deposited on the conductive substrate to form upright SnS2 nanosheets. Therefore, the temperature parameters and distance parameters in the preparation method of the present application are important, and the upright SnS2 nanosheets cannot be obtained without the related temperature and distance;

[0053] S42, seal the two ends of the fourth quartz tube using flanges, noting that the gas inflow end is close to the sulfur powder side, and the gas outflow end is close to the conductive substrate side. Use a vacuum pump to pump the pressure in the fourth quartz tube to below 100Pa, which can exhaust the air in the fourth quartz tube to avoid the influence of air on the reaction process when heating, such as oxidation; then open the valves at the gas inflow end and outflow end, and continuously pass in 200sccm of argon for five minutes to further exhaust the air in the fourth quartz tube. The gas flow direction is from the sulfur powder end to the conductive substrate end, which can prevent oxidation during the reaction process; then adjust to pass in 30sccm of argon until the reaction is completed. The vacuum pump is always kept in working condition during the reaction to prevent air from entering, and because the deposition process can only occur at low pressure.

[0054] S43, the temperature of the constant-temperature heating zone of the heating furnace is set to 650℃. Since the temperature inside the fourth quartz tube is highest in the middle of the constant-temperature heating zone (650℃), and the temperature decreases closer to both ends of the fourth quartz tube, the temperature drop is less in the constant-temperature heating zone and more significant at the edge of the constant-temperature heating zone. Combining the positions and relative positions of sulfur powder, SnO2 powder, and conductive substrate in step S41, and considering that the sublimation temperature of SnO2 powder to gaseous state is 650℃, the sublimation temperature of sulfur powder to gaseous state is 200℃, and the deposition temperature of gaseous SnS2 on the conductive substrate is 300-380℃, when the temperature reaches 650℃, the SnO2 powder and sulfur powder inside the fourth quartz tube simultaneously vaporize, reacting to generate gaseous SnS2. Driven by argon gas, the generated SnS2 is deposited on the surface of the downstream conductive substrate, depositing as upright SnS2 nanosheets. Due to the high density, H-SnS2 nanosheets are formed, which are then removed after natural cooling.

[0055] Characterization and test results:

[0056] Figure 4 The Raman spectra of SnS2 obtained in step S33 of Example 3, MoS2 obtained in step S13 of Example 1, SnS2 / MoS2 heterojunction obtained in step S23 of Example 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2 are shown. Specifically, SnS2 has a Raman spectrum at 311.1 cm⁻¹. -1 The nearby characteristic peaks correspond to its A 1g Vibrational modes; monolayer MoS2 nanosheets at 383.9 cm⁻¹ -1 and 402.6cm -1 The characteristic peaks at E, respectively, correspond to E 2g and A 1g Vibration modes; in SnS2 / MoS2 heterojunctions and H-SnS2 / MoS2 heterojunctions, besides the A of SnS2 1g Beyond the peak, the E of MoS2 can also be clearly observed. 2g and A 1g Characteristic peaks. This indicates that the obtained heterojunctions are SnS2 / MoS2 heterojunctions and H-SnS2 / MoS2 heterojunctions, confirming the successful preparation of SnS2 / MoS2 heterojunctions and H-SnS2 / MoS2 heterojunctions.

[0057] Figure 5 The MoS2 obtained in step S13 of Example 1 ( Figure 5 a) H-SnS2 obtained in step S43 of Example 4 ( Figure 5 b) The SnS2 / MoS2 heterojunction obtained in step S23 of Example 1 ( Figure 5 c) The H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2 (Figure 5 d) optical and scanning electron microscope topography characterization. Figure 5 a is an optical microscope top view of MoS2 nanosheets obtained in step S13 of Example 1, large-area MoS2 nanosheets are randomly deposited on the conductive substrate, the length of the nanosheets is about 10-30 μm, and the coverage rate is 60%-70%. Figure 5 b is a scanning electron microscope side view of H-SnS2 obtained in step S43 of Example 4, the structure of H-SnS2 is a petal-like shape with high density, which has good contact with the substrate and maintains its vertical structure. Figure 5 c is a scanning electron microscope top view of SnS2 / MoS2 heterojunction obtained in step S23 of Example 1, the surface of the SnS2 / MoS2 heterojunction is a vertically grown SnS2 nanosheet, and the MoS2 nanosheet is laid at the bottom of the SnS2 nanosheet to form a van der Waals heterojunction. Since the SnS2 is vertically grown with high density, it is difficult to observe the MoS2 nanosheet at the bottom. Figure 5 d is a scanning electron microscope top view of H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2, the surface of the H-SnS2 / MoS2 heterojunction is a vertically grown SnS2 nanosheet, and the MoS2 nanosheet is laid at the bottom of the SnS2 nanosheet to form a van der Waals heterojunction. Since the SnS2 is vertically grown with high density, it is difficult to observe the MoS2 nanosheet at the bottom. Figure 6 Compared with the SnS2 / MoS2 heterojunction in c, the H-SnS2 / MoS2 heterojunction has higher density and open morphology. The above illustrates the successful preparation of the SnS2 / MoS2 heterojunction and the H-SnS2 / MoS2 heterojunction, and the SnS2 nanosheet is upright on the MoS2 nanosheet.

[0058] Figure 7 is the photocurrent density curve of the PEC type photodetector based on MoS2 obtained in step S13 of Example 1, SnS2 obtained in step S33 of Example 3, H-SnS2 obtained in step S43 of Example 4, SnS2 / MoS2 heterojunction obtained in step S23 of Example 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2 under different light powers under simulated sunlight at 0 V bias. The incident light powers corresponding to the I-VI regions are 200, 150, 100, 75, 50, and 20 mW / cm 2, the horizontal axis represents time, and the vertical axis represents the size of the photocurrent density. Under any of the above light powers, the photocurrent response of the PEC type photodetector based on the SnS2 / MoS2 heterojunction and the H-SnS2 / MoS2 heterojunction is greater than that of the PEC type photodetector based on the SnS2 or MoS2 nanosheet, indicating that the built-in electric field in the formed SnS2 / MoS2 heterojunction makes the separation and transmission process of the photo-generated carriers faster, and thus the photoelectric response is stronger, so the photoelectric performance of the PEC type photodetector based on the SnS2 / MoS2 heterojunction is higher. The photocurrent response of the PEC type photodetector based on the SnS2 / MoS2 heterojunction and the H-SnS2 / MoS2 heterojunction is compared, and the response of the latter is greater, which indicates that more upright SnS2 nanosheets on the MoS2 nanosheet can make the specific surface area of the H-SnS2 / MoS2 heterojunction larger, on the one hand, more photo-generated carriers are generated, and on the other hand, the strength of the built-in electric field between the MoS2 nanosheet is greater, therefore, the response of the PEC type photodetector based on the H-SnS2 / MoS2 heterojunction is greater, and the photoelectric performance such as the accuracy of photoelectric detection is higher. As can be seen from the figure, the photocurrent response of the PEC type photodetector based on the H-SnS2 / MoS2 heterojunction is as high as 932.8 μA / cm 2 , which is about 377 times that of pure SnS2.

[0059] Figure 7 is the photocurrent density (I ph ) and the photoresponse rate (R ph ) figure of the PEC type photodetector based on the MoS2 obtained in step S13 of embodiment 1, the SnS2 obtained in step S33 of embodiment 3, the H-SnS2 obtained in step S43 of embodiment 4, the SnS2 / MoS2 heterojunction obtained in step S23 of embodiment 1, and the H-SnS2 / MoS2 heterojunction obtained in step S23 of embodiment 2 under different light powers of simulated sunlight at 0V bias. The horizontal axis is different incident light powers, which are 200, 150, 100, 75, 50, 20 mW / cm 2 , and the left vertical axis is I ph , and the left vertical axis is R ph . Specifically, the difference between the bright current and the dark current and the effective light area ratio under bright and dark environments is I ph (I ph =(I light -I dark ) / S; R ph is calculated by the ratio of I ph to the corresponding light power (R ph =I ph / P). I ph and R phA higher value indicates a stronger light response, better photoelectric detection performance, and higher photoelectric detection accuracy. Figure 8 It can be seen that, under different incident light powers, the IC of PEC-type photodetectors based on SnS2 / MoS2 heterojunction and H-SnS2 / MoS2 heterojunction varies. ph and R ph All of these values ​​are greater than those of PEC-type photodetectors based on MoS2 nanosheets, SnS2 nanosheets, and H-SnS2 nanosheets. This indicates that the built-in electric field within the formed SnS2 / MoS2 heterojunction enables faster separation and transport of photogenerated carriers, resulting in a stronger photoelectric response. Therefore, the PEC-type photodetector based on the SnS2 / MoS2 heterojunction has higher photoelectric performance, including higher accuracy. The I values ​​of the PEC-type photodetector based on the H-SnS2 / MoS2 heterojunction are shown below for different incident light powers. ph and R ph The photoresponse of the H-SnS2 / MoS2 heterojunction-based PEC photodetector is significantly improved compared to PEC photodetectors based on MoS2 nanosheets, SnS2 nanosheets, H-SnS2 nanosheets, and SnS2 / MoS2 heterojunctions. This indicates that the higher density of upright SnS2 nanosheets on the MoS2 nanosheets results in a larger specific surface area for the H-SnS2 / MoS2 heterojunction, leading to more photogenerated carriers and further accelerating carrier separation and transfer. Therefore, the SnS2 / MoS2-based PEC photodetector proposed in this application exhibits higher photoelectric performance, including higher photodetection accuracy.

[0060] Figure 8 This is a photocurrent density curve showing the illumination / darkness variation of PEC-type photodetectors based on the following: MoS2 obtained in step S13 of Example 1, SnS2 obtained in step S33 of Example 3, H-SnS2 obtained in step S43 of Example 4, SnS2 / MoS2 heterojunction obtained in step S23 of Example 1, and H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2, under 0V bias voltage illumination. Figure 9 It can be seen that all photodetectors have a strong response to visible light, and the optical power is 10mW / cm². 2Specifically, the photocurrent density of the PEC type photoelectric detector based on the SnS2 / MoS2 heterojunction and the H-SnS2 / MoS2 heterojunction is greater than that of the PEC type photoelectric detector based on the MoS2 nanosheet, the SnS2 nanosheet and the H-SnS2 nanosheet, which indicates that the built-in electric field in the formed SnS2 / MoS2 heterojunction makes the separation and transmission process of the photo-generated carriers faster and the response stronger, and indicates that the wavelength sensitivity and accuracy of the PEC type photoelectric detector based on the SnS2 / MoS2 heterojunction are higher. The photocurrent density corresponding to the PEC type photoelectric detector based on the H-SnS2 / MoS2 heterojunction is greater than that of the PEC type photoelectric detector based on the SnS2 / MoS2 heterojunction, which indicates that more high-density upright SnS2 nanosheets on the MoS2 nanosheet can make the specific surface area of the H-SnS2 / MoS2 heterojunction larger, on the one hand, more photo-generated carriers are generated, and on the other hand, the strength of the built-in electric field between the MoS2 nanosheet and the H-SnS2 / MoS2 heterojunction is greater. Therefore, it is indicated that the PEC type photoelectric detector based on the SnS2 / MoS2 heterojunction has stronger photoelectric response in the visible light band and higher detection sensitivity and accuracy of different wavelengths of light.

[0061] Figure 9 The photocurrent density and photoresponse rate of the PEC type photoelectric detector based on the MoS2 obtained in step S13 of embodiment 1, the SnS2 obtained in step S33 of embodiment 3, the H-SnS2 obtained in step S43 of embodiment 4, the SnS2 / MoS2 heterojunction obtained in step S23 of embodiment 1 and the H-SnS2 / MoS2 heterojunction obtained in step S23 of embodiment 2 at different wavelengths under 0V bias are shown in the following figures, and the light power is 10mW / cm 2 The abscissa is different wavelengths, which are 350nm, 380nm, 420nm, 450nm, 475nm, 500nm, 520nm, 550nm, 600nm and 650nm, and the left ordinate is I ph , and the left ordinate is R ph It can be seen from Figure 10 that under all the above wavelengths, the I ph and R phAll of them are greater than the PEC type photodetector based on MoS2 nanosheet, SnS2 nanosheet and H-SnS2 nanosheet, which indicates that the built-in electric field in the SnS2 / MoS2 heterojunction makes the separation and transmission process of photo-generated carriers faster and the response stronger, and indicates that the wavelength sensitivity and accuracy of the PEC type photodetector based on the SnS2 / MoS2 heterojunction are higher. Under all the above wavelengths, compared with the PEC type photodetector based on the SnS2 / MoS2 heterojunction, the light response of the PEC type photodetector based on the H-SnS2 / MoS2 heterojunction is greatly improved, which indicates that more high-density upright SnS2 nanosheets on the MoS2 nanosheet can make the specific surface area of the H-SnS2 / MoS2 heterojunction larger, and more photo-generated carriers are generated, further accelerating the carrier separation and transfer process. Therefore, it is indicated that the PEC type photodetector based on SnS2 / MoS2 proposed in the application has higher light detection accuracy and wavelength sensitivity in the visible light band.

[0062] Figure 10 The response / recovery time diagram and summary diagram of the PEC type photodetector based on MoS2 obtained in step S13 of embodiment 1, SnS2 obtained in step S33 of embodiment 3, H-SnS2 obtained in step S43 of embodiment 4, SnS2 / MoS2 heterojunction obtained in step S23 of embodiment 1 and H-SnS2 / MoS2 heterojunction obtained in step S23 of embodiment 2 under 0V bias are shown in the following figure. The response time (t res ) and recovery time (t rec ) are the time when the photocurrent reaches stability when the excitation light is incident or the light is turned off, that is, the response time of the photocurrent from 10% (90%) to 90% (10%), and the shorter the response / recovery time, the faster the response of the photodetector, and thus the higher the sensitivity of the photodetector. Figure 10 a is the response / recovery time diagram of the PEC type photodetector based on the H-SnS2 / MoS2 heterojunction under 0V bias, wherein the response time and the recovery time are extremely fast, and are 3.6ms and 6.4ms, respectively, in the order of milliseconds. Figure 11b is the response / recovery time of each photodetector. The response / recovery time of the PEC photodetector based on the SnS2 / MoS2 heterojunction and the H-SnS2 / MoS2 heterojunction is shorter than that of the PEC photodetector based on the MoS2 nanosheet, the SnS2 nanosheet and the H-SnS2 nanosheet, which indicates that the built-in electric field in the SnS2 / MoS2 heterojunction makes the separation and transport process of the photo-generated carriers faster, and the response faster, and indicates that the sensitivity and accuracy of the PEC photodetector based on the SnS2 / MoS2 heterojunction are higher. Compared with the PEC photodetector based on the SnS2 / MoS2 heterojunction, the response / recovery time of the PEC photodetector based on the H-SnS2 / MoS2 heterojunction is shorter, which indicates that more high-density upright SnS2 nanosheets on the MoS2 nanosheet can make the specific surface area of the H-SnS2 / MoS2 heterojunction larger, and the photo-generated carriers produced are more, further accelerating the separation and transport process of the carriers. Therefore, it is indicated that the PEC photodetector based on the SnS2 / MoS2 heterojunction has a faster photoelectric response, and a higher light detection accuracy and sensitivity.

[0063] The reference electrode mercury-mercurous sulfate in the PEC photodetector based on the SnS2 / MoS2 heterojunction in Example 1 is replaced by a silver-silver chloride electrode, and the photoelectrocatalytic hydrogen production can be realized.

[0064] Figure 11 The photoelectrocatalytic hydrogen production results of the PEC photodetector based on the MoS2 obtained in step S13 of Example 1, the SnS2 obtained in step S33 of Example 3, the H-SnS2 obtained in step S43 of Example 4, the SnS2 / MoS2 heterojunction obtained in step S23 of Example 1 and the H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2 are shown in FIG. 6. Figure 12 As shown in FIG. 6, under the external bias of 0.8 V, the incident light power is 100 mW / cm 2The hydrogen yields of PEC-type photodetectors based on SnS2 / MoS2 heterojunctions and H-SnS2 / MoS2 heterojunctions were higher than those based on MoS2 nanosheets, SnS2 nanosheets, and H-SnS2 nanosheets, indicating that the photoelectrocatalytic system based on SnS2 / MoS2 heterojunctions had better photoelectrocatalytic performance and could be applied to photoelectrocatalysis. Compared to the photoelectrocatalytic system based on SnS2 / MoS2 heterojunctions, the photoelectrocatalytic system based on H-SnS2 / MoS2 heterojunctions had a higher hydrogen yield, indicating that the higher density of upright SnS2 nanosheets on the MoS2 nanosheets was beneficial to improving the photoelectrocatalytic effect. Specifically, the hydrogen yield of the photoelectrocatalytic system based on H-SnS2 / MoS2 heterojunctions reached 6.8 μmol / cm³ within 2.5 h. -2 The concentrations are 1 to 6 times higher than those of other samples. Therefore, this demonstrates that the SnS2 / MoS2-based PEC photodetector proposed in this application can be used in the field of photoelectrocatalysis.

[0065] Figure 12 This is a comparison chart of the photoelectrocatalytic / photocatalytic / electrocatalytic hydrogen production effects of the PEC-type photodetector based on the H-SnS2 / MoS2 heterojunction obtained in step S23 of Example 2. ​ As shown, the hydrogen production capacity of the photoelectrocatalytic system based on the H-SnS2 / MoS2 heterojunction PEC photodetector is 6.79 μmol / cm³. -2 The total amount of hydrogen produced is greater than that produced by photocatalysis and electrocatalysis. This may be due to the synergistic effect that accelerates charge separation and transport, indicating that the PEC-type photodetector based on the H-SnS2 / MoS2 heterojunction has good photoelectrocatalytic performance and can be applied to photoelectrocatalysis.

[0066] In practical applications, the photocurrent density (I) is utilized. ph ) and photoresponsivity (R ph Its photodetector performance can be quantitatively evaluated. The photoresponse calculation formula is: photocurrent density I ph =(I light -I dark ) / S,I light The magnitude of the photocurrent under illumination, I dark Photocurrent refers to the magnitude of the photocurrent in a dark environment (no light), and S refers to the area of ​​the heterojunction (working electrode) illuminated by light. Photoresponsivity R ph =I ph / P,I ph Let P be the photocurrent density and P be the incident light power.

[0067] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A PEC-type photodetector based on SnS2 / MoS2, characterized in that, The photodetector includes an electrolyte tank, a reference electrode, a working electrode, and a counter electrode. The fixed ends of the reference electrode, the working electrode, and the counter electrode are all fixed to the cover of the electrolyte tank through snap-fit ​​holes. The free ends of the reference electrode, the working electrode, and the counter electrode are all suspended inside the electrolyte tank, and none of the free ends of the reference electrode, the working electrode, and the counter electrode are in contact with the bottom of the electrolyte tank. The working electrode includes a conductive substrate, a MoS2 layer, and a SnS2 layer. The MoS2 layer is in contact with the conductive substrate, and the SnS2 layer is disposed on the side of the MoS2 layer away from the conductive substrate. That is, the working substance of the working electrode is a SnS2 / MoS2 heterojunction. The plane of the SnS2 nanosheets in the SnS2 layer is perpendicular to the plane of the MoS2 nanosheets in the MoS2 layer. The size of the MoS2 nanosheets is 10-30 μm, and the coverage of the MoS2 nanosheets is 60-70%. The SnS2 / MoS2 heterojunction was prepared by the following steps: S1, MoS2 nanosheets were prepared on a conductive substrate using chemical vapor deposition. Using sulfur powder and MoO3 powder as precursors, MoS2 nanosheets were grown on the conductive substrate at a growth temperature of 680℃ and a growth pressure of 450Pa. S2, SnS2 nanosheets grown on the conductive substrate with MoS2 nanosheets obtained in step S1 as the deposition substrate. Using sulfur powder and SnCl4·5H2O powder as precursors, SnS2 nanosheets are grown on the conductive substrate on which the MoS2 nanosheets are grown in step S1, at a growth temperature of 450℃. Argon gas is introduced during both steps S1 and S2 until the deposition reaction is completed, and the vacuum pump is in operation during the growth process.

2. The PEC-type photodetector based on SnS2 / MoS2 according to claim 1, characterized in that, The SnS2 / MoS2 heterojunction is opposite to the light-transmitting window on the electrolyte tank.

3. The PEC-type photodetector based on SnS2 / MoS2 according to claim 2, characterized in that, The reference electrode is made of mercury-mercurous sulfate.

4. The PEC-type photodetector based on SnS2 / MoS2 according to claim 3, characterized in that, The material of the counter electrode is platinum.

5. The PEC-type photodetector based on SnS2 / MoS2 according to claim 4, characterized in that, The conductive substrate is either an indium-doped tin oxide transparent conductive ITO substrate or a fluorine-doped tin oxide transparent conductive FTO substrate.

6. The PEC-type photodetector based on SnS2 / MoS2 according to claim 5, characterized in that, The reference electrode, the working electrode, and the counter electrode are all arranged perpendicularly to the bottom of the electrolyte tank.

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