Z-type heterojunction composite material of tungsten oxide nanorod/titanium carbide quantum dot/indium sulfide nanosheet, preparation method therefor and application thereof

Abstract

Disclosed are a Z-type heterojunction composite material of a tungsten oxide nanorod/a titanium carbide quantum dot/an indium sulfide nanosheet, a preparation method therefor and an application thereof. The method includes: preparing a titanium carbide quantum dot by using freeze-thaw and ultrasound methods for multiple times, and then placing a tungsten trioxide nanorod prepared by a hydrothermal method into a titanium carbide quantum dot aqueous solution, stirring same, and then standing same to obtain a tungsten oxide nanorod loading a quantum dot; stirring and uniformly mixing an indium compound and a sulfur compound in an ethylene glycol solvent, and then adding the tungsten oxide nanorod loading the quantum dot, and performing a reflux reaction at constant temperature to obtain the composite material. The titanium carbide quantum dot of the present invention can provide good electron transport channels at different semiconductor interfaces.

Claims

1. A method of preparing a WO.sub.3/Ti.sub.3C.sub.2 QDs (quantum dots)/In.sub.2S.sub.3 Z-scheme heterojunction composite material, comprising: preparing Ti.sub.3C.sub.2 QDs by a freeze-thaw-ultrasonic method; preparing WO.sub.3 nanorods by a hydrothermal method; immersing the WO.sub.3 nanorods in an aqueous solution of the Ti.sub.3C.sub.2 QDs and stirring to obtain WO.sub.3 nanorods loaded with QDs; and refluxing the WO.sub.3 nanorods loaded with QDs, an indium compound, and a sulfur compound in a solvent to obtain the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction composite material.

2. The method of claim 1, wherein the indium compound is InCl.sub.3.Math.4H.sub.2O or In(NO.sub.3).sub.3.Math.4.5H.sub.2O; the sulfur compound is sodium sulfide nonahydrate, thioacetamide, or thiourea; and the solvent is an alcohol solvent.

3. The method of claim 1, wherein the WO.sub.3 nanorods loaded with QDs, the indium compound, and the sulfur compound are refluxed at 90-105 C. for 1-2 hours.

4. The method of claim 1, wherein the WO.sub.3 nanorods are obtained by the hydrothermal reaction of sodium tungstate dihydrate, sodium chloride, hydrochloric acid and water.

5. The method of claim 4, wherein the hydrothermal reaction is conducted at 160-180 C. for 24-28 hours.

6. The method of claim 1, wherein the Ti.sub.3C.sub.2 QDs are prepared by etching Ti.sub.3AlC.sub.2 with a mixture of lithium fluoride and hydrochloric acid and subjecting the Ti.sub.3AlC.sub.2 to a freeze-thaw treatment and a water bath ultrasonic treatment.

7. The method of claim 6, wherein the water bath ultrasonic treatment is conducted with an output power of 150-300 W for 1-2 hours.

8. The method of claim 6, wherein the freeze-thaw treatment is conducted before the water bath ultrasonic treatment and repeated 2-6 times.

9. The method of claim 8, wherein the freeze-thaw treatment includes refrigerating the Ti.sub.3AlC.sub.2 at 0-5 C., freezing the Ti.sub.3AlC.sub.2 at 80-20 C., and thawing Ti.sub.3AlC.sub.2 at room temperature.

10. The WO.sub.3/Ti.sub.3C.sub.2 QDs (quantum dots)/In.sub.2S.sub.3 Z-scheme heterojunction composite material prepared according to the method of claim 1.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 TEM image of titanium carbide quantum dots (Ti.sub.3C.sub.2 QDs);

(2) FIG. 2 SEM image of Tungsten trioxide nanorod (WO.sub.3 nanorods);

(3) FIG. 3 TEM image of tungsten trioxide nanorods loaded with titanium carbide quantum dots (WO.sub.3/Ti.sub.3C.sub.2 QDs);

(4) FIG. 4 SEM image of Z-scheme heterojunction of tungsten oxide nanorods/titanium carbide quantum dots/indium sulfide nanosheets (WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3);

(5) FIG. 5 The photocatalytic degradation curves of BPA for WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3;

(6) FIG. 6 The photocatalytic degradation curves of Cr (VI) for WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3.

SPECIFIC EXAMPLES METHOD

(7) The present invention uses simple preparation methods to construct Z-scheme heterojunction composite material with 0D QDs, 1D nanorods, and 2D nanosheets for the degradation of hexavalent chromium and bisphenol A. Among them, 0D transition metal carbide quantum dots with good metal-like conductivity are a good dielectric material.

(8) As traditional semiconductor materials, tungsten trioxide, and indium sulfide have been widely used in the field of catalysis, but the treatment effect of pollutants in water needs to be improved. In the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction disclosed in the present invention, the combination of Ti.sub.3C.sub.2 QDs with excellent conductivity as the electron transfer medium can extend the ultraviolet response of the WO.sub.3 with a wide band gap to the visible light region. At the same time, it also solves the problem of easy agglomeration of nano-scale materials and greatly improves the utilization rate of the photogenerated electron.

(9) The invention provided a preparation method of WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction. The steps are as follows: Ti.sub.3C.sub.2 quantum dots are prepared by a freeze-thaw-ultrasonic method, and then the WO.sub.3 nanorods prepared by the hydrothermal method re placed in an aqueous solution of Ti.sub.3C.sub.2 QDs. The components are stirred and then allowed to stand to obtain the tungsten oxide nanorods loaded with quantum dots. After the indium compound and the sulfur compound re stirred and mixed uniformly, the above-mentioned quantum dot-loaded tungsten oxide nanorods are added and the reaction is refluxed at a constant temperature to obtain WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction.

(10) The Ti.sub.3C.sub.2 QDs of the present invention can provide excellent electron transmission channels at different semiconductor interfaces, and the as-obtained composite material can directly absorb and utilize visible light, which solves the problem that WO.sub.3 only generates light response in the ultraviolet light region.

(11) The starting materials involved in the present invention are all commercially available conventional products. Simultaneously the specific operation methods and test methods are all conventional in the field. If the temperature and gas environment are not specified, they are all carried out at room temperature.

Examples 1: Preparation of Ti.SUB.3.C.SUB.2 .QDs

(12) In the centrifuge tube, 0.8 g of lithium fluoride was added to 10 mL of 9 mol/L hydrochloric acid, and then 0.45 g of titanium carbide aluminide was added. Then the sample was stirred for a while at room temperature for etching, the reaction product was washed to pH 6. Immediately afterward, deionized water was added again, and the layered titanium carbide solution was obtained by shaking it by hand for 10 minutes. Argon gas was bubbled into the titanium carbide solution in the centrifuge tube for 5 minutes, then the freeze-thaw operation was performed 5 times: The sample was first placed in a refrigerator at 4 C. for 3 h, then placed in another refrigerator at 40 C. for 3 h, and finally placed in a room temperature environment to thaw. So far, one freeze-thaw process has been completed, and this process was repeated 4 more times. After 5 times of freeze-thaw operation, the layered titanium carbide solution was sonicated at 150 W for 1 h at room temperature to obtain a solution containing titanium carbide flakes and quantum dots. This solution was filtered three times through a 0.22 m microporous membrane to filter out the flake titanium carbide, and finally, an aqueous solution (100 mg/L) containing a large amount of Ti.sub.3C.sub.2 QDs was obtained, which was used in Examples 3.

(13) FIG. 1 is TEM image of titanium carbide quantum dots (Ti.sub.3C.sub.2 QDs) obtained above. From the above figure, it can be clearly seen that the Ti.sub.3C.sub.2 QDs have relatively high content and are uniformly dispersed.

Examples 2: Preparation of WO.SUB.3 .Nanorods

(14) 0.825 g of Na.sub.2WO.sub.4.Math.2H.sub.2O and 0.4 g of NaCl were added to 20 mL of deionized water and stirred for 30 min. 3 mol/L hydrochloric acid solution was added dropwise to the above solution, and the pH meter was used to detect during the dropwise addition to make the solution pH=2. Then the solution was transferred to the reactor for the hydrothermal reaction. The hydrothermal reaction temperature was 180 C., and the hydrothermal time was 24 hours to obtain a dispersion of tungsten trioxide nanorods. After centrifugal washing, it was placed in a 65 C. drying oven and dried overnight to obtain WO.sub.3 nanorods powder.

(15) FIG. 2 is SEM image of the WO.sub.3 obtained above. It can be seen from the above figure that the WO.sub.3 has a nanorod structure and is uniformly dispersed.

Examples 3: Preparation of WO.SUB.3./Ti.SUB.3.C.SUB.2 .QDs/In.SUB.2.S.SUB.3 .Z-Scheme Heterojunction

(16) 0.1 g of the WO.sub.3 nanorods powder of Examples 2 was added to 120 mL of Ti.sub.3C.sub.2 QDs aqueous solution. The mixture was stirred (1000 rpm) in a vacuum environment for 12 h and then lyophilized to obtain quantum dot-loaded WO.sub.3 nanorods powder. 57.95 mg (1 mmol) of quantum dot-loaded WO.sub.3 powder was dispersed in 10 mL of ethylene glycol, and 205 mg (2.8 mmol) of InCl.sub.3.Math.4H.sub.2O was dissolved in 15 mL of ethylene glycol. The two solutions were mixed in the flask, and 79 mg (4.2 mmol) of thioacetamide was added. Then the flask was connected to the spherical condenser and the three-way valve, and the interface was sealed. Firstly, the air in the flask and condenser tube was sucked away by the vacuum pump, and then argon was blown in. Finally, the above device was placed in an oil bath at 95 C. and refluxed for 90 min. After the reflux, the flask was put into an ice-water mixture to quickly cool down, and the cooled reaction product was washed and dried to a constant weight in a vacuum drying oven to obtain WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction.

(17) FIG. 3 is TEM image of WO.sub.3/Ti.sub.3C.sub.2 QDs, and FIG. 4 is SEM image of Z-scheme heterojunction of WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3. It can be seen from the above figure that the quantum dots are uniformly loaded on the tungsten trioxide nanorods. WO.sub.3In.sub.2S.sub.3 and WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 are similar in appearance after growing In.sub.2S.sub.3 nanosheets on WO.sub.3 nanorods.

Control Examples 1: Preparation of Ti.SUB.3.C.SUB.2 .QDs by Ultrasonic Method

(18) The layered Ti.sub.3C.sub.2 solution obtained according to the method of Examples 1 was placed in a centrifuge tube, and argon was continuously bubbled in for 5 minutes, then it was sonicated at 150 W at room temperature for 1 hour to obtain an aqueous solution containing Ti.sub.3C.sub.2 nanosheets and quantum dots. This solution was filtered through a 0.22 m microporous membrane three times to remove large pieces of Ti.sub.3C.sub.2, and finally, an aqueous solution of titanium carbide quantum dots of uniform size (55 mg/L) was obtained. It can be seen that in parallel experiments, the yield was lower than the freeze-thaw-ultrasonic method.

(19) The layered titanium carbide solution obtained according to the method of Examples 1. Afterward, argon gas was bubbled into the titanium carbide solution in the centrifuge tube for 5 minutes, then the freeze-thaw operation was performed 5 times: The sample was placed in a refrigerator at 40 C. for 3 h, and placed in a room-temperature environment to thaw. So far, one freeze-thaw process has been completed, and this process was repeated 4 more times. After 5 times of freeze-thaw operation, the layered titanium carbide solution was sonicated at 150 W for 1 h at room temperature to obtain a solution containing titanium carbide flakes and quantum dots. This solution was filtered three times through a 0.22 microporous membrane to filter out the flake titanium carbide, and finally, an aqueous solution (75 mg/L) containing a large amount of Ti.sub.3C.sub.2 QDs was obtained.

Control Examples 2: Preparation of In.SUB.2.S.SUB.3 .Nanosheets

(20) 205 mg of InCl.sub.3.Math.4H.sub.2O was dissolved in 15 mL of ethylene glycol, then 79 mg of thioacetamide was added. The reactants were then placed in an oil bath and refluxed at 95 C. for 90 min. After the reflux, the flask was placed in a mixture of ice and water to quickly cool down. The cooled reaction product was washed with a mixed solvent of ethanol and water and then dried to a constant weight in a vacuum drying oven to obtain In.sub.2S.sub.3 nanosheets.

Control Examples 3: Preparation of WO.SUB.3.In.SUB.2.S.SUB.3

(21) 0.1 g of the WO.sub.3 powder of Examples 2 was dispersed in 10 mL of ethylene glycol, and another 205 mg of InCl.sub.3.Math.4H.sub.2O was dissolved in 15 mL of ethylene glycol. The two evenly dispersed solutions were uniformly mixed, then 79 mg of thioacetamide was added. The reactants were then placed in an oil bath and refluxed at 95 C. for 90 min. After the reflux, the flask was placed in a mixture of ice and water to quickly cool down. The cooled reaction product was washed with a mixed solvent of ethanol and water and then dried to a constant weight in a vacuum drying oven to obtain WO.sub.3In.sub.2S.sub.3.

Examples 4: Photocatalytic Activity of WO.SUB.3./Ti.SUB.3.C.SUB.2 .QDs/In.SUB.2.S.SUB.3 .Evaluated by Degradation of Bisphenol A

(22) 10 mg of the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction obtained above was placed in 10 mL of Bisphenol A aqueous solution with a concentration of 10 mg/L. BPA was adsorbed for 60 min under dark conditions to reach adsorption equilibrium. After equilibration, a 300 W xenon lamp was used as the light source, and 1 mL of the solution was taken every 15 minutes. The solution was filtered with a 0.22 water-based filter and added to the high-performance liquid sample bottle. The sample was tested with a high-performance liquid chromatograph in the mobile phase of deionized water:methanol=3:7 (volume ratio) for the absorption curve at 290 nm ultraviolet wavelength. At the same time, the peak area of Bisphenol A at about 6 min was recorded, and the initial concentration of Bisphenol A was marked as 100% to obtain the photodegradation curve of Bisphenol A.

(23) FIG. 5 is the photocatalytic degradation curves of BPA for WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3. The first 60 minutes is the adsorption equilibrium time under dark conditions. It can be seen from the figure that with the increase of visible light irradiation time, the concentration of Bisphenol A gradually decreases, and the removal rate of Bisphenol A after 120 min of irradiation reaches 97.6%.

(24) Under the same test conditions, the removal rates of Bisphenol A in the water were about 10%, 40%, and 75% after WO.sub.3 (Examples 2), In.sub.2S.sub.3 (Control Examples 2), and WO.sub.3In.sub.2S.sub.3 (Control Examples 3) were illuminated for 120 min.

(25) The dosages of InCl.sub.3.Math.4H.sub.2O and thioacetamide in Examples 3 were adjusted to 176 mg (2.4 mmol) and 67 mg (3.6 mmol), respectively. The other conditions remain unchanged, and the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction was obtained. The sample was tested using the same method. After 120 min of light, the removal rate of Bisphenol A in the water was 69%.

(26) The dosages of InCl.sub.3.Math.4H.sub.2O and thioacetamide in Examples 3 were adjusted to 234 mg (3.2 mmol) and 90 mg (4.8 mmol), respectively. The other conditions remain unchanged, and the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction was obtained. The sample was tested using the same method. After 120 min of light, the removal rate of Bisphenol A in the water was 71%.

Examples 5: Photocatalytic Activity of WO.SUB.3./Ti.SUB.3.C.SUB.2 .QDs/In.SUB.2.S.SUB.3 .Evaluated by Degradation of Cr (VI)

(27) 5 mg of the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction obtained above was placed in 20 mL 10 mg/L potassium dichromate aqueous solution (chromium ion concentration 20 mg/L). Cr (VI) was adsorbed for 60 min under dark conditions to reach adsorption equilibrium. After equilibration, a 300 W xenon lamp was used as the light source, and 1 mL of the solution was taken every 3 minutes. The solution was filtered with a 0.22 m water-based filter and added to the centrifuge tube. After the chromogenic agent was added, the sample was detected by an ultraviolet spectrophotometer, and the degradation efficiency of hexavalent chromium is calculated from the absorbance. The initial concentration of Cr (VI) was marked as 100%. With the increase of light time, the concentration of Cr (VI) gradually decreased with the gradual decrease of absorbance, thus obtaining a specific degradation curve of Cr (VI).

(28) FIG. 6 is the photocatalytic degradation curves of Cr (VI) for WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3. The first 60 minutes is the adsorption equilibrium time under dark conditions. It can be seen from the figure that the absorbance of Cr (VI) gradually decreases with the prolonging of the illumination time, indicating that the concentration of Cr (VI) in the water is also decreasing. After 15 minutes of visible light irradiation, the Cr (VI) is completely removed. Under the same test conditions, the removal rates of Cr (VI) in the water were about 21%, 54%, and 87% after WO.sub.3 (Examples 2), In.sub.2S.sub.3(Control Examples 2), and WO.sub.3In.sub.2S.sub.3(Control Examples 3) were illuminated for 120 min.

(29) The dosages of InCl.sub.3.Math.4H.sub.2O and thioacetamide in Examples 3 were adjusted to 176 mg (2.4 mmol) and 67 mg (3.6 mmol), respectively. The other conditions remain unchanged, and the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction was obtained. The sample was tested using the same method. After 15 min of light, the removal rate of Cr (VI) in the water was 80%.

(30) The dosages of InCl.sub.3.Math.4H.sub.2O and thioacetamide in Examples 3 were adjusted to 234 mg (3.2 mmol) and 90 mg (4.8 mmol), respectively. The other conditions remain unchanged, and the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction was obtained. The sample was tested using the same method. After 15 min of light, the removal rate of Cr (VI) in the water was 73%.

(31) Ti.sub.3C.sub.2 and Ti.sub.3C.sub.2 QDs have no catalytic effect and cannot catalytically remove Bisphenol A and Cr (VI). Under visible light, compared with WO.sub.3 nanorods, the catalytic effects of WO.sub.3/Ti.sub.3C.sub.2 QDs on Bisphenol A and Cr (VI) were not improved, and the removal rate is only 11% and 24%.

(32) In the present invention, Ti.sub.3C.sub.2 QDs are used as the electron transfer medium. Firstly, a mild etching method was used to prepare a preliminary layered Ti.sub.3C.sub.2 solution, and then the Ti.sub.3C.sub.2 QDs were efficiently prepared by a simple method of multiple freeze-thaw and ultrasound. Immediately, the solution was allowed to stand, so that the quantum dots were evenly loaded on the surface of the WO.sub.3 nanorods, and finally, the WO.sub.3/Ti.sub.3C.sub.2 QDs/In.sub.2S.sub.3 Z-scheme heterojunction was constructed by the reflow method. The as-obtained material has strong absorption in the visible light region of 400-600 nm, which improves the utilization rate of sunlight. At the same time, the Z-scheme heterojunction structure constructed by introducing OD Ti.sub.3C.sub.2 QDs has significantly enhanced photocatalytic activity.