BISMUTH TUNGSTATE/BISMUTH SULFIDE/MOLYBDENUM DISULFIDE HETEROJUNCTION TERNARY COMPOSITE MATERIAL AND PREPARATION METHOD AND APPLICATION THEREOF

Abstract

The present invention relates to a bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material and a preparation method and application thereof. The composite material is composed of bismuth tungstate, bismuth sulfide and molybdenum disulfide in an ordered layered way, Bi.sub.2WO.sub.6 is an orthorhombic system, Bi.sub.2S.sub.3 is a p-type semiconductor located on a (130) crystal face, MoS.sub.2 is a layered transition metal sulfide located on a (002) crystal face, the whole composite material is of a spherical structure with an unsmooth surface, and a layer of nanosheets uniformly grow on an outer layer. The average particle size of composite materials is in the range of 2.4-2.6 μm. The spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material prepared in the present invention has good adsorption of Cr(VI) and high catalytic reduction ability under visible light.

Claims

1. A bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material, composed of bismuth tungstate, bismuth sulfide and molybdenum disulfide in an ordered layered way, wherein Bi.sub.2WO.sub.6 is an orthorhombic system, Bi.sub.2S.sub.3 is a p-type semiconductor located on a (130) crystal face, MoS.sub.2 is a layered transition metal sulfide located on a (002) crystal face, the whole composite material is of a spherical structure with an unsmooth surface, and a layer of nanosheets uniformly grow on an outer layer; the average particle size of composite materials is in the range of 2.4-2.6 μm.

2. A preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 1, wherein the method comprises: preparing a spherical bismuth tungstate, dispersing the spherical bismuth tungstate in water, adding Na.sub.2MoO.sub.4.2H.sub.2O and thiourea, and preforming a hydrothermal reaction on the mixed solution to obtain a reaction product, which is the Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material.

3. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 2, wherein a preparation method of the spherical bismuth tungstate comprises: adding bismuth nitrate pentahydrate and PVP K30 into a mixed solution of water, absolute ethanol and glacial acetic acid to obtain a mixed solution A; and mixing an aqueous solution B of sodium tungstate dihydrate and the mixed solution A to obtain a mixed solution b, and then performing a solvothennal reaction on the mixed solution b to obtain the spherical bismuth tungstate.

4. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 3, wherein a mass ratio of bismuth nitrate pentahydrate to PVP K30 is (0.2-0.25):1.

5. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 3, wherein a volume ratio of water to absolute ethanol to glacial acetic acid in the mixed solution of water, absolute ethanol and glacial acetic acid is (2-4):1:1.

6. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 3, wherein a molar ratio of Bi(NO.sub.3).sub.3.5H.sub.2O to Na.sub.2WO.sub.4.2H.sub.2O in the mixed solution b is (1.5-2.5):1.

7. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 3, wherein the solvothermal reaction temperature is 150-200° C., and the reaction time is 15-20 hours.

8. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 2, wherein an adding ratio of spherical Bi.sub.2WO.sub.6 to Na.sub.2MoO.sub.4.2H.sub.2O to thiourea is 200 mg:(0.075-0.30) g:(0.15-0.60).

9. The preparation method of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 2, wherein the hydrothermal reaction condition is 180-220° C., and the reaction time is 22-26 hours.

10. Application of the bismuth tungstate/bismuth sulfide/molybdenum disulfide heterojunction ternary composite material according to claim 1 in catalytic materials, sensing materials, photoelectric materials, magnetic materials, electronic materials and energy storage materials.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows X-ray diffraction (XRD) patterns of spherical Bi.sub.2WO.sub.6 and spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 prepared in Embodiment 3 of the present invention;

[0026] FIG. 2(a) is a scanning electron microscope (SEM) image of spherical Bi.sub.2WO.sub.6 prepared in Embodiment 3 of the present invention;

[0027] FIG. 2(b) is a transmission electron microscope (TEM) image of spherical Bi.sub.2WO.sub.6 prepared in Embodiment 3 of the present invention;

[0028] FIG. 3(a) is a scanning electron microscope (SEM) image of spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 prepared in Embodiment 3 of the present invention;

[0029] FIG. 3(b) is a transmission electron microscope (TEM) image of spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 prepared in Embodiment 3 of the present invention;

[0030] FIG. 4 is a high-resolution transmission electron microscope (HRTEM) image of spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 prepared in Embodiment 3 of the present invention;

[0031] FIG. 5 shows the effect of removing 40 mg L.sup.−1 Cr(VI) (based on K.sub.2Cr.sub.2O.sub.7) under visible light by samples prepared in Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention (the use amount of a catalyst is 0.4 g L.sup.−1).

DESCRIPTION OF THE EMBODIMENTS

[0032] It should be pointed out that the following detailed descriptions are all illustrative and are intended to provide further descriptions of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those usually understood by a person of ordinary skill in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are merely for describing specific implementations, and are not intended to limit exemplary implementations according to this application. As used herein, the singular form is also intended to include the plural form unless the context clearly dictates otherwise. In addition, it should be further understood that, terms “comprise” and/or “include” used in this specification indicate that there are features, steps, operations, devices, components, and/or combinations thereof.

Embodiment 1

[0034] (1) Preparation of spherical Bi.sub.2WO.sub.6

[0035] A solution A and a solution B were prepared during synthesis of a spherical Bi.sub.2WO.sub.6 precursor. 2 mmol of Bi(NO.sub.3).sub.3.5H.sub.2O and 4 g of PVP K30 were added into 50 mL of a mixed solution of water, absolute ethanol and glacial acetic acid (volume ratio 3:1:1) and stirred at room temperature until the solution was clear to obtain the solution A. 1 mmol of Na.sub.2WO.sub.4.2H.sub.2O was added into 20 mL of H.sub.2O and subjected to ultrasonic treatment for 30 minutes to obtain the solution B. The solution B was added dropwise into the solution A and stirred for 60 minutes to obtain a uniform suspension. The suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a solvothermal reaction at 180° C. for 18 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a light yellow Bi.sub.2WO.sub.6 powder.

[0036] (2) Preparation of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material

[0037] 200 mg of the Bi.sub.2WO.sub.6 powder was dispersed into 40 mL of water by ultrasonic treatment. 0.075 g of Na.sub.2MoO.sub.4.2H.sub.2O and 0.15 g of thiourea were added and stirred for 1 hour. The obtained uniform suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a hydrothermal reaction at 200° C. for 24 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material. The product obtained according to this adding ratio was named as BBM-20 for convenient description.

Embodiment 2

[0038] (1) Preparation of spherical Bi.sub.2WO.sub.6

[0039] A solution A and a solution B were prepared during synthesis of a spherical Bi.sub.2WO.sub.6 precursor. 2 mmol of Bi(NO.sub.3).sub.3.5H.sub.2O and 4 g of PVP K30 were added into 50 mL of a mixed solution of water, absolute ethanol and glacial acetic acid (volume ratio 3:1:1) and stirred at room temperature until the solution was clear to obtain the solution A. 1 mmol of Na.sub.2WO.sub.4.2H.sub.2O was added into 20 mL of H.sub.2O and subjected to ultrasonic treatment for 30 minutes to obtain the solution B. The solution B was added dropwise into the solution A and stirred for 60 minutes to obtain a uniform suspension. The suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a solvothermal reaction at 180° C. for 18 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a light yellow Bi.sub.2WO.sub.6 powder.

[0040] (2) Preparation of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material

[0041] 200 mg of the Bi.sub.2WO.sub.6 powder was dispersed into 40 mL of water by ultrasonic treatment. 0.13 g of Na.sub.2MoO.sub.4.2H.sub.2O and 0.26 g of thiourea were added and stirred for 1 hour.

[0042] The obtained uniform suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a hydrothermal reaction at 200° C. for 24 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material. The product obtained according to this adding ratio was named as BBM-30 for convenient description.

Embodiment 3

[0043] (1) Preparation of spherical Bi.sub.2WO.sub.6

[0044] A solution A and a solution B were prepared during synthesis of a spherical Bi.sub.2WO.sub.6 precursor. 2 mmol of Bi(NO.sub.3).sub.3.5H.sub.2O and 4 g of PVP K30 were added into 50 mL of a mixed solution of water, absolute ethanol and glacial acetic acid (volume ratio 3:1:1) and stirred at room temperature until the solution was clear to obtain the solution A. 1 mmol of Na.sub.2WO.sub.4.2H.sub.2O was added into 20 mL of H.sub.2O and subjected to ultrasonic treatment for 30 minutes to obtain the solution B. The solution B was added dropwise into the solution A and stirred for 60 minutes to obtain a uniform suspension. The suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a solvothermal reaction at 180° C. for 18 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a light yellow Bi.sub.2WO.sub.6 powder.

[0045] (2) Preparation of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material

[0046] 200 mg of the Bi.sub.2WO.sub.6 powder was dispersed into 40 mL of water by ultrasonic treatment, 0.20 g of Na.sub.2MoO.sub.4.2H.sub.2O and 0.40 g of thiourea were added and stirred for 1 hour. The obtained uniform suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a hydrothermal reaction at 200° C. for 24 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material. The product obtained according to this adding ratio was named as BBM-40 for convenient description.

[0047] The morphology and structure of prepared samples were characterized by XRD, SEM, TEM and HRTEM, as shown in FIG. 1, FIG. 2, FIG. 3 and FIG. 4.

[0048] FIG. 1 shows XRD patterns of spherical Bi.sub.2WO.sub.6 and spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 prepared in Embodiment 3 of the present invention. Pure Bi.sub.2WO.sub.6 has diffraction peaks when 20 is 28.299°, 32.790°, 47.138°, 55.990°, 58.538°, 68.754°, 76.075° and 78.534°, crystal face diffraction is (131), (200), (202), (133), (262), (400), (2102) and (204) and is consistent with the JCPDS 39-0256 standard card, and Pure Bi.sub.2WO.sub.6 belongs to an orthorhombic system. For spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2, a diffraction peak at 25° corresponds to a (130) crystal face of Bi.sub.2S.sub.3, and a diffraction peak at 32° can be ascribed to a (100) crystal face of MoS.sub.2. It is shown through XRD results that pure-phase spherical Bi.sub.2WO.sub.6 and a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 ternary composite material are successfully prepared.

[0049] FIG. 2(a) is an SEM image of spherical Bi.sub.2WO.sub.6 prepared in Embodiment 3 of the present invention, and FIG. 2(b) is a TEM image of spherical Bi.sub.2WO.sub.6 prepared in Embodiment 3 of the present invention. As shown in the figures, single Bi.sub.2WO.sub.6 is of a spherical structure self-assembled from nanosheets and has a particle size of about 2.5 μm.

[0050] FIG. 3(a) is an SEM image of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material prepared in Embodiment 3 of the present invention, and FIG. 3(b) is a TEM image of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material prepared in Embodiment 3 of the present invention. As shown in the figures, Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 is of a spherical structure. Compared with Bi.sub.2WO.sub.6, the particle size is not changed significantly, and a layer of nanosheets uniformly grow on an outer layer. It can be found by comparing FIGS. 2(a) and 3(a) that different from pure Bi.sub.2WO.sub.6, the nanosheets on the surface of the composite material are curled and low in thickness, and thus it can be seen that other substances grow on the surfaces of Bi.sub.2WO.sub.6 microspheres.

[0051] FIG. 4 is an HRTEM image of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material prepared in Embodiment 3 of the present invention. It can be seen from the figures that a Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material is successfully prepared.

Embodiment 4

[0052] (1) Preparation of spherical Bi.sub.2WO.sub.6

[0053] A solution A and a solution B were prepared during synthesis of a spherical Bi.sub.2WO.sub.6 precursor. 2 mmol of Bi(NO.sub.3).sub.3.5H.sub.2O and 4 g of PVP K30 were added into 50 mL of a mixed solution of water, absolute ethanol and glacial acetic acid (volume ratio 3:1:1) and stirred at room temperature until the solution was clear to obtain the solution A. 1 mmol of Na.sub.2WO.sub.4.2H.sub.2O was added into 20 mL of H.sub.2O and subjected to ultrasonic treatment for 30 minutes to obtain the solution B. The solution B was added dropwise into the solution A and stirred for 60 minutes to obtain a uniform suspension. The suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a solvothermal reaction at 180° C. for 18 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a light yellow Bi.sub.2WO.sub.6 powder.

[0054] (2) Preparation of a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material

[0055] 200 mg of the Bi.sub.2WO.sub.6 powder was dispersed into 40 mL of water by ultrasonic treatment. 0.30 g of Na.sub.2MoO.sub.4.2H.sub.2O and 0.60 g of thiourea were added and stirred for 1 hour.

[0056] The obtained uniform suspension was transferred into a 100 mL polytetrafluoroethylene lined autoclave for a hydrothermal reaction at 200° C. for 24 hours. After natural cooling to room temperature, centrifugation, washing, drying and grinding were performed to obtain a spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite material The product obtained according to this adding ratio was named as BBM-50 for convenient description.

Embodiment 5

[0057] The photocatalytic performance of the spherical Bi.sub.2WO.sub.6/Bi.sub.2S.sub.3/MoS.sub.2 heterojunction ternary composite as a photocatalytic material was evaluated by reducing Cr(VI) under visible light. The process was as follows: a catalyst (0.4 g L.sup.−1) was added into a Cr(VI) solution (40 mg L.sup.−1, based on Cr(VI) in a K.sub.2Cr.sub.2O.sub.7 solution). Then, the pH value of an initial solution was adjusted to 2 with 1 M HCl solution. Ultrasonic treatment was performed for 4 minutes. Before irradiation, a suspension was stirred for 60 minutes in a dark place to establish an adsorption-desorption balance. During irradiation with a xenon lamp (300 W, 2 higher than 400 nm), 3 mL of the suspension was taken from a reaction vessel at a regular interval and centrifuged (9,000 r min.sup.−1, 10 minutes), and then a supernatant was collected with a 0.22 μm filter membrane syringe to remove residual particles. At last, the absorbance at 540 nm at different times was measured by using a diphenylcarbazide (DPC) method so as to obtain the concentration of Cr(VI).

[0058] FIG. 5 shows the effect of removing 40 mg L.sup.−1 Cr(VI) under visible light in Embodiment 5 (samples Bi.sub.2WO.sub.6, BBM-20, BBM-30, BBM-40 and BBM-50) of the present invention. It can be seen from the figure that BBM-40 has the best photocatalytic performance.

[0059] It can be seen from tests on the products in the embodiments that with the increased addition amount of Na.sub.2MoO.sub.4.2H.sub.2O and thiourea, the morphology of materials growing on the Bi.sub.2WO.sub.6 microspheres are changed from nanoparticles into nanosheets. When 0.20 g of Na.sub.2MoO.sub.4.2H.sub.2O and 0.40 g of thiourea are added, a layer of nanosheets grow uniformly on the surface of Bi.sub.2WO.sub.6. However, when the addition amount of the Mo source and S source is further increased, MoS.sub.2 aggregates on the surface of a sample can be clearly observed. At the same time, with the increased addition amount of Na.sub.2MoO.sub.4.2H.sub.2O and thiourea, the ability of the composite material for photocatalytic reduction of Cr(VI) is first improved and then reduced. According to exploration of a series of influencing factors, it is found by the inventors that experimental conditions in Embodiment 3 of the present invention are the optimal conditions, and a product has a regular morphology and high photocatalytic reduction ability.

[0060] According to a Chinese patent with an application publication number of CN 105753054 A (application number 201610082396.8), a microspherical three-dimensional hierarchical micro-nano-structured bismuth tungstate photocatalytic material and a preparation method thereof are disclosed. According to the method, sodium tungstate dihydrate and bismuth nitrate pentahydrate are used as raw materials, the pH of a solution is adjusted to 1 with nitric acid in a preparation process, an experimental process is relatively cumbersome and high in energy consumption, and a large amount of strongly acidic waste liquid is produced after a reaction, resulting in environmental pollution. Compared with this patent, the experimental process of the present invention is simpler, easy to operate, safe and free of pollution.

[0061] The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art may make various modifications and changes to the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.