Preparation method and application of a zinc sulfide polytype heterojunction photocatalyst

Abstract

The present invention discloses a preparation method and application of a zinc sulfide homogeneous heterojunction photocatalyst. First, wurtzite zinc sulfide is synthesized by a hydrothermal method, and then wurtzite zinc sulfide is successfully loaded onto ZIF-L through in-situ composite. The composite is in-situ sulfided to synthesize a zinc sulfide homogeneous heterojunction. The formation of the homogeneous heterojunction significantly inhibits the recombination of photo-generated electron-hole pairs. Compared with pure zinc sulfide, the photocatalytic hydrogen production performance is significantly improved. In particular, the impedance value of the zinc sulfide homogeneous heterojunction photocatalyst prepared in Example 2 is significantly reduced, the separation efficiency of photo-generated electron-hole pairs is significantly improved, and the photocatalytic hydrogen production performance is as high as 24.7 mmol / g.

Description

Technical Field

[0001] The present invention belongs to the technical field of the synthesis of semiconductor photocatalytic materials, and particularly relates to a preparation method and application of a zinc sulfide heterophase junction photocatalyst. Background Art

[0002] Due to the rapid growth of industrialization and population, global environmental deterioration and energy shortage have become two major problems in today's society. Therefore, the demand for clean and efficient energy is extremely urgent. Hydrogen is a carbon-neutral energy carrier that can replace the increasingly scarce fossil fuels. Solar-driven photocatalytic water splitting for hydrogen evolution is considered a promising strategy and effective approach to meet the growing demand for green and renewable energy and solve global environmental problems. In the past few decades, semiconductor photocatalytic hydrogen production technology has been widely developed. However, due to the rapid recombination of wide-bandgap photo-generated electron-hole pairs and low light utilization efficiency, the photocatalytic efficiency of the studied semiconductors is still inhibited.

[0003] Zinc sulfide (ZnS) mainly exists in the form of cubic sphalerite and hexagonal wurtzite, and is widely used in semiconductor photocatalysts due to its high photocatalytic hydrogen production activity. In addition, due to the relatively negative conduction band potential of the photo-induced electrons of ZnS, even in the absence of noble metal cocatalysts, its photo-induced electrons have an impressive ability to reduce protons to H2. Due to the excellent transmission performance, high electron mobility, non-toxicity, insolubility in water, and relatively low price of ZnS, it is considered an important photocatalyst for hydrogen production. However, the high recombination of electron-hole pairs limits the performance of the photocatalyst, and this situation can be solved by constructing a junction. Constructing a junction is an effective means to regulate the bandgap and absorption characteristics.

[0004] The present invention affects the dispersion degree of zinc sulfide nanospheres by regulating the loading amount of wurtzite zinc sulfide on ZIF-L, and then sulfidation achieves the purpose that different contents of heterophase junctions have different effects on the photocatalytic hydrogen production performance. Its photoelectrochemical test shows that the separation efficiency of photo-generated electron-hole pairs is significantly improved. At present, there is no relevant report on the research of constructing a zinc sulfide homophase heterojunction to improve the photocatalytic hydrogen production performance. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a preparation method of a zinc sulfide homophase heterojunction photocatalyst. The zinc sulfide heterojunction prepared by this method can visually observe wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L sheets from the morphology. When it is used as a photocatalyst in the experiment of photocatalytic water splitting for hydrogen production, it shows excellent photocatalytic hydrogen production performance and good cycle stability.

[0006] The present invention adopts the following technical solutions to solve the above technical problems. A preparation method of a zinc sulfide polytype heterojunction photocatalyst is characterized in that the specific process is as follows:

[0007] Step S1: Dissolve zinc acetate hexahydrate in deionized water, then add thiourea and polyvinylpyrrolidone, stir and mix evenly at room temperature, and then transfer to a polytetrafluoroethylene high-pressure reaction kettle and react at 130-150 °C. After the reaction is completed, centrifuge to collect the sample to obtain wurtzite zinc sulfide nanospheres;

[0008] Step S2: Add the wurtzite zinc sulfide nanospheres obtained in Step S1 and zinc nitrate hexahydrate to deionized water according to a molar ratio of 1:1 to 1:3. After ultrasonic dispersion and mixing evenly, add 2-methylimidazole and stir and react at room temperature. After the reaction is completed, centrifuge, wash, and place in an oven to dry to obtain a composite sample of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L;

[0009] Step S3: Add the composite sample prepared in Step S2 to a mixed aqueous solution containing sodium sulfite and sodium sulfide, stir and react at room temperature, centrifuge and wash, and place in an oven to dry to obtain a zinc sulfide polytype heterojunction photocatalyst. The impedance value of this zinc sulfide polytype heterojunction photocatalyst is significantly reduced, the separation efficiency of photogenerated electron-hole pairs is significantly improved, and the photocatalytic hydrogen production performance is as high as 24.7 mmol / g.

[0010] Further defined, the specific process of Step S1 is: Add 0.99 g of zinc acetate hexahydrate to deionized water, stir at room temperature until completely dissolved, then add 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone, stir and mix evenly, and then transfer to a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene lining. Place the reaction kettle in a blast drying oven and react at 140 °C. After the reaction is completed, naturally cool to room temperature, centrifuge, and wash three times with water and ethanol respectively. The obtained sample is dried in a blast drying oven at 60 °C to obtain wurtzite zinc sulfide nanospheres.

[0011] Further defined, the specific process of Step S2 is: Add 0.99 g of zinc nitrate hexahydrate to deionized water, stir until completely dissolved, then add 0.0980-0.2940 g of wurtzite zinc sulfide nanospheres, ultrasonically disperse and mix evenly, and then add to an aqueous solution containing 2.9550 g of 2-methylimidazole, stir and react at room temperature. After the reaction is completed, centrifuge, and wash three times with water and methanol respectively. The obtained sample is dried in a blast drying oven at 60 °C to obtain a composite sample of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L.

[0012] Further defined, the mass of the wurtzite zinc sulfide nanospheres is 0.1960 g.

[0013] Further defined, the length of the leaf-shaped ZIF-L is 4-5 μm.

[0014] Further defined, the specific process of step S3 is as follows: Add 0.0200 g of the composite sample of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L into a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite, stir and react at room temperature, centrifuge, wash three times with water and ethanol respectively, and dry the obtained sample in a forced-air drying oven at 60 °C to obtain the target product zinc sulfide polytype photocatalyst.

[0015] Application of the zinc sulfide polytype photocatalyst described in the present invention as a photocatalytic water splitting hydrogen production catalyst.

[0016] The present invention has the following advantages and beneficial effects compared with the prior art: The present invention first synthesizes wurtzite zinc sulfide nanospheres by a one-step hydrothermal method, affects the dispersion degree of zinc sulfide on ZIF-L by regulating the molar ratio of zinc ions in wurtzite zinc sulfide nanospheres and ZIF-L, and then in-situ sulfides to obtain a zinc sulfide polytype photocatalyst; when this material is used as a catalyst for photocatalytic water splitting hydrogen production, the existence of the polytype junction greatly improves the separation efficiency of photogenerated electron-hole pairs, and its hydrogen production performance is significantly improved. Description of the Drawings

[0017] Figure 1 It is a scanning electron microscope image of wurtzite zinc sulfide W and zinc sulfide polytype W / S prepared in Example 2. (a) and (b) wurtzite zinc sulfide W, (c) and (d) zinc sulfide polytype W / ZIF-L, W is dispersed on the surface of ZIF-L.

[0018] Figure 2 It is an X-ray diffraction pattern of wurtzite zinc sulfide W, zinc sulfide polytype W / S and S prepared in Example 2. It can be seen from the figure that the zinc sulfide polytype has the existence of (100) and (101) crystal planes of wurtzite zinc sulfide W, and also the existence of (111) and (200) crystal planes of sphalerite zinc sulfide S.

[0019] Figure 3 It is a photocatalytic hydrogen production performance diagram of wurtzite zinc sulfide W, zinc sulfide polytype W / S and S prepared in Example 2. It can be seen from the figure that the hydrogen production amount of zinc sulfide polytype W / S is 2.1 times that of wurtzite zinc sulfide W and 5.9 times that of sphalerite zinc sulfide S.

[0020] Figure 4 It is an electrochemical impedance spectroscopy diagram of wurtzite zinc sulfide W, zinc sulfide polytype W / S and S prepared in Example 2. It can be seen from the figure that the zinc sulfide polytype W / S has the smallest charge transfer resistance. Detailed Embodiments

[0021] The above content of the present invention will be further described in detail through the following examples. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. Any technology implemented based on the above content of the present invention belongs to the scope of the present invention.

[0022] Example 1

[0023] Weigh 0.99 g of zinc acetate hexahydrate and add it to 40 mL of deionized water. Stir at room temperature for 10 min until completely dissolved. Weigh 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone and add them to the above solution. After stirring for 30 min, transfer the mixed solution to a stainless-steel autoclave lined with polytetrafluoroethylene. Then, place the autoclave in a forced-air drying oven and react at 140 °C for 5 h. After the experiment ends, naturally cool to room temperature, and centrifuge (8000 r·min -1 , 4 min), wash three times with water and ethanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C for 10 h to obtain wurtzite zinc sulfide W. Weigh 0.99 g of zinc nitrate hexahydrate and add it to 90 mL of deionized water. Stir until completely dissolved. Weigh 0.0980 g of wurtzite zinc sulfide and add it to the above mixed solution. Ultrasonically disperse for 1 h. Add the mixed system to 90 mL of an aqueous solution containing 2.9550 g of 2-methylimidazole. Stir and react at room temperature for 5 h. After the reaction ends, centrifuge (7000 r·min -1 , 5 min), wash three times with water and methanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C for 10 h to obtain a composite sample W / ZIF-L with wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L. Weigh 0.0200 g of W / ZIF-L and add it to 50 mL of a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite. Stir and react at room temperature for 3 h, centrifuge, wash three times with water and ethanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C to obtain the target product, zinc sulfide polytype photocatalyst, to obtain zinc sulfide polytype W / S.

[0024] Example 2

[0025] Weigh 0.99 g of zinc acetate hexahydrate and add it to 40 mL of deionized water. Stir at room temperature for 10 min until completely dissolved. Weigh 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone and add them to the above solution. After stirring for 30 min, transfer the mixed solution to a stainless-steel autoclave lined with polytetrafluoroethylene. Then, place the autoclave in a forced-air drying oven and react at 140 °C for 5 h. After the experiment ends, naturally cool to room temperature, and centrifuge (8000 r·min -1, 4 min), washed three times with water and ethanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C for 10 h to prepare wurtzite zinc sulfide W. Weigh 0.99 g of zinc nitrate hexahydrate and add it to 90 mL of deionized water, stir until completely dissolved, weigh 0.1960 g of wurtzite zinc sulfide and add it to the above mixed solution, ultrasonically disperse for 1 h, add the mixed system to 90 mL of an aqueous solution containing 2.9550 g of 2-methylimidazole, and stir at room temperature for 5 h. After the reaction is completed, centrifuge (7000 r·min -1 , 5 min), washed three times with water and methanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C for 10 h to obtain a composite sample W / ZIF-L with wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L. Weigh 0.0200 g of W / ZIF-L and add it to 50 mL of a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite, stir at room temperature for 3 h, centrifuge, wash three times with water and ethanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C to prepare the target product zinc sulfide polytype heterojunction photocatalyst to obtain zinc sulfide polytype heterojunction W / S.

[0026] Example 3

[0027] Weigh 0.99 g of zinc acetate dihydrate and add it to 40 mL of deionized water, stir at room temperature for 10 min until completely dissolved, weigh 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone and add them to the above solution, stir for 30 min, then transfer the mixed solution to a stainless steel autoclave lined with polytetrafluoroethylene, and then put the autoclave into a blast drying oven and react at 140 °C for 5 h. After the experiment is completed, naturally cool to room temperature, centrifuge (8000 r·min -1 , 4 min), washed three times with water and ethanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C for 10 h to prepare wurtzite zinc sulfide W. Weigh 0.99 g of zinc nitrate hexahydrate and add it to 90 mL of deionized water, stir until completely dissolved, weigh 0.2940 g of wurtzite zinc sulfide and add it to the above mixed solution, ultrasonically disperse for 1 h, add the mixed system to 90 mL of an aqueous solution containing 2.9550 g of 2-methylimidazole, and stir at room temperature for 5 h. After the reaction is completed, centrifuge (7000 r·min -1, 5 min), washed three times with water and methanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C for 10 h to obtain a composite sample W / ZIF-L of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L. Weigh 0.0200 g of W / ZIF-L and add it to 50 mL of a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite, stir and react at room temperature for 3 h, centrifuge, wash three times with water and ethanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C to obtain the target product zinc sulfide polytype heterojunction photocatalyst to obtain zinc sulfide polytype heterojunction W / S

[0028] Example 4

[0029] Weigh 0.99 g of zinc acetate hexahydrate and add it to 40 mL of deionized water, stir at room temperature for 10 min until completely dissolved. Weigh 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone and add them to the above solution. After stirring for 30 min, transfer the mixed solution to a stainless steel autoclave lined with polytetrafluoroethylene, and then put the autoclave into a blast drying oven and react at 140 °C for 4 h. After the experiment, cool it to room temperature naturally, centrifuge (8000 r·min -1 , 4 min), washed three times with water and ethanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C for 10 h to obtain wurtzite zinc sulfide W. Weigh 0.99 g of zinc nitrate hexahydrate and add it to 90 mL of deionized water, stir until completely dissolved. Weigh 0.1960 g of wurtzite zinc sulfide and add it to the above mixed solution, ultrasonically disperse for 1 h, add the mixed system to 90 mL of an aqueous solution containing 2.9550 g of 2-methylimidazole, stir and react at room temperature for 5 h. After the reaction, centrifuge (7000 r·min -1 , 5 min), washed three times with water and methanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C for 10 h to obtain a composite sample W / ZIF-L of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L. Weigh 0.0200 g of W / ZIF-L and add it to 50 mL of a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite, stir and react at room temperature for 3 h, centrifuge, wash three times with water and ethanol respectively, and the obtained sample was dried in a blast drying oven at 60 °C to obtain the target product zinc sulfide polytype heterojunction photocatalyst to obtain zinc sulfide polytype heterojunction W / S

[0030] Example 5

[0031] Weigh 0.99 g of zinc acetate hexahydrate and add it to 40 mL of deionized water. Stir at room temperature for 10 min until completely dissolved. Weigh 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone and add them to the above solution. After stirring for 30 min, transfer the mixed solution into a stainless-steel autoclave with a polytetrafluoroethylene liner. Then, place the autoclave in a forced-air drying oven and react at 140 °C for 6 h. After the experiment ends, naturally cool to room temperature, and centrifuge (8000 r·min -1 , 4 min), wash three times with water and ethanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C for 10 h to obtain wurtzite zinc sulfide W. Weigh 0.99 g of zinc nitrate hexahydrate and add it to 90 mL of deionized water. Stir until completely dissolved. Weigh 0.1960 g of wurtzite zinc sulfide and add it to the above mixed solution. Ultrasonically disperse for 1 h. Add the mixed system to 90 mL of an aqueous solution containing 2.9550 g of 2-methylimidazole. Stir and react at room temperature for 5 h. After the reaction ends, centrifuge (7000 r·min -1 , 5 min), wash three times with water and methanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C for 10 h to obtain a composite sample W / ZIF-L with wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L. Weigh 0.0200 g of W / ZIF-L and add it to 50 mL of a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite. Stir and react at room temperature for 3 h. Centrifuge, wash three times with water and ethanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C to obtain the target product, a zinc sulfide heterophase junction photocatalyst, to obtain a zinc sulfide heterophase junction W / S.

[0032] In this invention, wurtzite zinc sulfide is synthesized by the hydrothermal method. Then, through in-situ composite, wurtzite zinc sulfide is successfully loaded onto ZIF-L. The composite is in-situ sulfided to synthesize a zinc sulfide heterophase junction. The formation of the heterophase junction significantly inhibits the recombination of photo-generated electron-hole pairs. Compared with pure zinc sulfide, the photocatalytic hydrogen production performance is significantly improved. In particular, for the zinc sulfide heterophase junction photocatalyst prepared in Example 2, the impedance value is significantly reduced, the separation efficiency of photo-generated electron-hole pairs is significantly improved, and the photocatalytic hydrogen production performance is as high as 24.7 mmol / g.

[0033] The above examples describe the basic principles, main features, and advantages of this invention. Those skilled in the art should understand that this invention is not limited by the above examples. What is described in the above examples and the specification only illustrates the principles of this invention. Without departing from the scope of the principles of this invention, this invention will have various changes and improvements, and these changes and improvements all fall within the scope of protection of this invention.

Claims

1. A preparation method of a zinc sulfide polytype heterojunction photocatalyst, characterized in that The specific process is as follows: Step S1: Add 0.99 g of zinc acetate hexahydrate to deionized water, stir at room temperature until completely dissolved, then add 2.2836 g of thiourea and 0.4801 g of polyvinylpyrrolidone. After stirring and mixing evenly, transfer it to a stainless-steel autoclave with a polytetrafluoroethylene lining. Place the autoclave in a forced-air drying oven and react at 140 °C. After the reaction is completed, cool it naturally to room temperature, centrifuge, wash it three times with water and ethanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C to obtain wurtzite zinc sulfide nanospheres; Step S2: Add 0.99 g of zinc nitrate hexahydrate to deionized water, stir until completely dissolved, then add 0.1960 g of wurtzite zinc sulfide nanospheres, ultrasonically disperse and mix evenly, and then add it to an aqueous solution containing 2.9550 g of 2-methylimidazole. Stir and react at room temperature. After the reaction is completed, centrifuge, wash it three times with water and methanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C to obtain a composite sample of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L; Step S3: Add 0.0200 g of the composite sample of wurtzite zinc sulfide dispersed on leaf-shaped ZIF-L to a mixed aqueous solution containing 1.3657 g of sodium sulfide and 1.5755 g of sodium sulfite. Stir and react at room temperature, centrifuge, wash it three times with water and ethanol respectively. The obtained sample is dried in a forced-air drying oven at 60 °C to obtain the target product, zinc sulfide heterophase junction photocatalyst. The impedance value of this zinc sulfide heterophase junction photocatalyst is significantly reduced, the separation efficiency of photogenerated electron-hole pairs is significantly improved, and the photocatalytic hydrogen production performance is as high as 24.7 mmol / g.

2. The preparation method of the zinc sulfide polytype heterojunction photocatalyst according to claim 1, characterized in that The length of the leaf-shaped ZIF-L is 4 - 5 μm.

3. Application of the zinc sulfide polytype heterojunction photocatalyst prepared by the method according to claim 1 or 2 as a photocatalytic water splitting hydrogen production catalyst.

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