A method for preparing a ZnSe / ZnS heterojunction photocatalyst by a sulfidation method

Abstract

The application discloses a method for preparing a ZnSe / ZnS heterojunction photocatalyst by a sulfuration method, and comprises the following steps: firstly, ZnSe nanorods are prepared by using a grazing angle deposition technology in a closed cavity; and then, the ZnSe nanorod sample is placed in a tubular furnace to perform a sulfuration treatment, so as to obtain the ZnSe / ZnS heterojunction photocatalyst. The application has the characteristics of short preparation period, low cost, easy operation, environmental friendliness and the like, and has the basis for mass production. The heterojunction photocatalytic material obtained by using the method not only greatly improves the specific surface area and increases the active sites, but also significantly improves the photoelectric catalytic capability of the material by using the characteristics of the heterojunction.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photoelectric catalytic materials, in particular to a method for preparing a ZnSe / ZnS heterojunction photocatalyst through sulfuration. BACKGROUND

[0002] Green clean energy is in short supply and environmental pollution is increasingly serious, and therefore, it is urgent to find renewable clean energy. A semiconductor photocatalyst has great research value in solving energy and environmental problems, and many photocatalysts for decomposing water to produce hydrogen have been developed. However, how to further realize high-efficiency, visible-light, low-cost and stable photocatalytic materials is still a research hotspot. Among many catalytically active materials, CdS and CdSe nanocrystals, which belong to chalcogenides, have excellent catalytic effects. Although the catalytic activity and stability are extremely remarkable, the application of the materials is greatly limited by the toxicity and carcinogenicity of Cd. Therefore, excellent and environmentally friendly substitutes are widely studied. ZnSe is a stable non-noble metal direct band gap semiconductor material and has photocatalytic properties, but the reported visible light catalytic efficiency is still low. In addition, the current research on photocatalysts mainly focuses on material structure and morphology, and doping modification. Therefore, controllable synthesis of nano-structured ZnSe and its composite materials through structure design has important research value for improving the photocatalytic performance. SUMMARY

[0003] In view of the above problems, the application provides a method for preparing a ZnSe / ZnS heterojunction photocatalyst through sulfuration,

[0004] The application adopts the following technical scheme:

[0005] A method for preparing a ZnSe / ZnS heterojunction photocatalyst through sulfuration comprises the following steps:

[0006] Step 1: preparing ZnSe nanorods;

[0007] Step 2: placing the ZnSe nanorods prepared in step 1 and sulfur powder in a multi-temperature zone tube furnace to perform sulfuration, so as to obtain a ZnSe / ZnS heterojunction photocatalyst.

[0008] Further, the specific steps for preparing the ZnSe nanorods in step 1 are as follows:

[0009] FTO glass is used as a substrate, and ZnSe particles are used as evaporation raw materials;

[0010] A vacuum is extracted from a closed cavity, and when the cavity pressure is reduced to 8x10 -4 Pa, deposition is started;

[0011] The angle between the substrate and the horizontal plane is adjusted, and the rotation speed of the substrate is set.

[0012] The evaporation rate of ZnSe is set.

[0013] Further, the step 2 specific method is that the sulfur powder is placed in the first temperature zone with a temperature of 250 DEG C, and the ZnSe nanorod is placed in the second temperature zone with a temperature of 250-350 DEG C; N2 is used as the carrier gas with a flow rate of 50 sccm, and the sulfuration time is 30-60 min, and after the sulfuration is completed, the natural cooling is performed to room temperature.

[0014] Further, the length of the ZnSe nanorod is 300-500 nm.

[0015] Further, the purity of the sulfur powder is 99.99%.

[0016] Further, the purity of the ZnSe particle is >99.9%.

[0017] Further, the included angle between the substrate and the horizontal plane is 83-86 DEG, and the rotation speed of the substrate is 1-3 r / min.

[0018] Further, the evaporation rate of ZnSe is

[0019] The present application has the beneficial effects of:

[0020] The method has the advantages of simple operation, high repeatability, low cost, environmental friendliness and the like. The obtained ZnSe / ZnS heterojunction has a nano structure, which effectively increases the specific surface area and active sites of the material; the heterojunction effectively promotes the separation of photo-generated carriers, thereby improving the photocatalytic performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described in the following are merely related to some embodiments of the present application, but not limit the present application.

[0022] Figure 1 is the sulfuration schematic diagram of the present application

[0023] Figure 2 is the SEM graph of ZnSe before sulfuration prepared by the test example 1 of the present application

[0024] Figure 3 is the XPS graph of the ZnSe / ZnS heterojunction photocatalyst prepared by the test example 1 of the present application

[0025] Figure 4 is the SEM graph of the ZnSe / ZnS heterojunction photocatalyst prepared by the test example 1 of the present application

[0026] Figure 5is a SEM image of the ZnSe / ZnS heterojunction photocatalyst prepared in Test Example 2 of the present application

[0027] Figure 6 is an I-V curve of the ZnSe / ZnS heterojunction photocatalyst prepared in Test Examples 1 and 2 of the present application DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative effort belong to the scope of protection of the present application.

[0029] The present application will be further described below with reference to the drawings and embodiments.

[0030] As shown in Figures 1 to 6 a method for preparing a ZnSe / ZnS heterojunction photocatalyst by a sulfuration method, characterized in that it comprises the following steps:

[0031] Step 1: preparing ZnSe nanorods.

[0032] The specific steps for preparing the ZnSe nanorods in Step 1 are as follows:

[0033] Using an electron beam evaporation device and a glancing angle deposition technique, first, FTO glass is used as a substrate, and ZnSe particles are used as evaporation raw materials, the purity of the ZnSe particles being >99.9%; then, a vacuum is extracted from a closed cavity, and deposition is started when the gas pressure in the cavity is reduced to 8×10 -4 Pa; the substrate is adjusted at an angle of 83-86° with the horizontal plane, and the rotation speed of the substrate is 1-3 r / min; and the evaporation rate of ZnSe is set, the evaporation rate of ZnSe being

[0034] Specifically, the length of the ZnSe nanorods is 300-500 nm, and the ZnSe nanorods are prepared to increase the specific surface area of the catalyst, and the contact area of the rod-shaped structure with the solution is larger.

[0035] Step 2: placing the ZnSe nanorods in Step 1 and sulfur powder in a multi-temperature zone tube furnace for sulfuration to obtain a ZnSe / ZnS heterojunction photocatalyst.

[0036] The specific method of step 2 is that the sulfur powder is placed in a first temperature zone with a temperature of 250°C, wherein the purity of the sulfur powder is 99.99%; the ZnSe nanorod is placed in a second temperature zone with a temperature of 250-350°C; N2 is used as a carrier gas with a flow rate of 50sccm, and the sulfuration time is 30-60min; after the sulfuration is completed, the sample is naturally cooled to room temperature.

[0037] Example 1

[0038] Step 1: ZnSe nanorods are prepared by using a glancing angle deposition technique of an electron beam evaporation device.

[0039] Further, FTO glass is used as a substrate, and ZnSe particles (purity >99.9%) are used as evaporation raw materials.

[0040] Further, a vacuum is extracted from the closed cavity, and the deposition is started when the gas pressure in the cavity is reduced to 8x10-4Pa. -4 Pa.

[0041] Further, the angle between the substrate and the horizontal plane is adjusted to 85°, and the rotation speed of the substrate is 1r / min.

[0042] Further, the evaporation rate of ZnSe is set to 0.1A. The length of the nanorod is 500nm.

[0043] Step 2: the ZnSe nanorod sample obtained in step 1 is placed in a multi-temperature zone tube furnace for sulfuration.

[0044] Further, a quartz boat containing sulfur powder is placed in a first temperature zone with a temperature of 250°C, and the ZnSe nanorod sample is placed in a second temperature zone; after the first temperature zone is stabilized for 10min, the second temperature zone reaches a specific temperature of 250°C.

[0045] Further, N2 is used as a carrier gas with a flow rate of 50sccm, and the sulfuration time is 30min.

[0046] Further, after the sulfuration is completed, the sample is naturally cooled to room temperature, and then taken out for measurement.

[0047] Example 2

[0048] Step 1: ZnSe nanorods are prepared by using a glancing angle deposition technique of an electron beam evaporation device.

[0049] Further, FTO glass is used as a substrate, and ZnSe particles (purity >99.9%) are used as evaporation raw materials.

[0050] Further, a vacuum is extracted from the closed cavity, and the deposition is started when the gas pressure in the cavity is reduced to 8x10-4Pa.

[0051] Further, the angle between the substrate and the horizontal plane is adjusted to 85°, and the rotation speed of the substrate is 1 r / min.

[0052] Further, the evaporation rate of ZnSe is set to 0.5 nm / min. The length of the nanorod is 500 nm.

[0053] Step 2: The ZnSe nanorod sample obtained in step 1 is placed in a multi-temperature zone tube furnace for sulfurization.

[0054] Further, a quartz boat containing sulfur powder is placed in the first temperature zone at a temperature of 250°C, and the ZnSe nanorod sample is placed in the second temperature zone. After the first temperature zone is stabilized for 10 min, the second temperature zone reaches a specific temperature of 300°C.

[0055] Further, N2 is used as the carrier gas at a flow rate of 50 sccm, and the sulfurization time is 30 min.

[0056] Further, after the sulfurization is completed, the sample is naturally cooled to room temperature and then taken out for measurement.

[0057] The ZnSe / ZnS heterojunction photocatalyst prepared in the example is characterized by multi-functional X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and I-V curve. The I-V test is measured in a three-electrode configuration with Ag / AgCl as the reference electrode; a Pt sheet is used as the counter electrode, and a ZnSe / ZnS sample is used as the working electrode; 0.1 mol / L KOH is used as the electrolyte; and the measurement is performed under simulated 100 mW / cm 2 of sunlight irradiation.

[0058] Figure 2 The SEM image of the ZnSe sample prepared in the test example 1 before sulfurization shows that the nanorods are uniformly distributed with gaps. Figure 3 The XPS image of the ZnSe / ZnS heterojunction photocatalyst prepared in the test example 1 of the application is used to verify the existence of elements and their valence states. The existence of Zn2p, S2p and Se3d indicates that both ZnSe and ZnS exist in the prepared catalyst sample, further proving the formation of ZnSe / ZnS heterojunction. Figure 4 and Figure 5 The SEM images of the ZnSe / ZnS heterojunction photocatalyst prepared in the test example 1 and example 2 of the application show that the surface morphology of the sample after sulfurization has changed, with sulfur powder attached to the nanorods, the gaps between the nanorods have become smaller, and the morphology of different sulfurization temperatures also differs. Figure 6The I-V curve of the ZnSe / ZnS heterojunction photocatalyst prepared in the present application for the test examples 1 and 2 shows that the photocurrent is obviously increased under light, and the photocurrent at different temperatures is not the same, indicating that the photocatalyst produces a large number of photo-generated carriers under light, which can benefit the photocatalysis.

[0059] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiment made according to the technical essence of the present application still belong to the scope of the technical solution of the present application.

Claims

1. A method for preparing ZnSe / ZnS heterojunction photocatalysts via sulfidation, characterized in that, Includes the following steps: Step 1: Prepare ZnSe nanorods; the ZnSe nanorods have a length of 300–500 nm; Step 2: The ZnSe nanorods and sulfur powder described in Step 1 are placed in a multi-temperature zone tube furnace for sulfidation to obtain a ZnSe / ZnS heterojunction photocatalyst. The sulfur powder is placed in the first temperature zone at 250°C, and the ZnSe nanorods are placed in the second temperature zone at 250–350°C. N2 is used as the carrier gas at a flow rate of 50 sccm, and the sulfidation time is 30–60 min. After sulfidation is completed, the mixture is naturally cooled to room temperature.

2. The method for preparing ZnSe / ZnS heterojunction photocatalyst by sulfidation according to claim 1, characterized in that, The specific steps for preparing ZnSe nanorods in step 1 are as follows: using FTO glass as a substrate and ZnSe particles as the evaporation raw material; drawing a vacuum into the sealed cavity, and starting deposition when the pressure inside the cavity drops to 8×10-4 Pa; adjusting the angle between the substrate and the horizontal plane, and setting the rotation speed of the substrate; and setting the ZnSe evaporation rate.

3. The method for preparing ZnSe / ZnS heterojunction photocatalyst by sulfidation according to claim 1, characterized in that, The sulfur powder has a purity of 99.99%.

4. The method for preparing ZnSe / ZnS heterojunction photocatalyst by sulfidation according to claim 2, characterized in that, The purity of the ZnSe particles is >99.9%.

5. The method for preparing ZnSe / ZnS heterojunction photocatalyst by sulfidation according to claim 2, characterized in that, The base has an angle of 83-86° with the horizontal plane, and the base rotates at a speed of 1-3 r / min.

6. The method for preparing ZnSe / ZnS heterojunction photocatalyst by sulfidation according to claim 2, characterized in that, The ZnSe evaporation rate is 1~4 Å / s.

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