A method for preparing and applying a WO3 / Cu2WS4 composite material

Abstract

This invention belongs to the field of photocatalysis technology, specifically relating to a method for preparing and applying a WO3 / Cu2WS4 composite material. Hydrochloric acid is slowly poured into a sodium tungstate dihydrate solution and stirred to obtain a mixture. The mixture is then transferred to a reaction vessel and heated for a hydrothermal reaction. After heating, the mixture is allowed to cool naturally, washed, and dried to obtain WO3 powder. The WO3 powder is dispersed in water and ultrasonically treated to obtain a WO3 solution. Copper chloride dihydrate and sodium tungstate dihydrate are dissolved in a solvent and stirred until dissolved. Then, a sulfur source and the WO3 solution are added, stirred, and mixed. The mixture is then transferred to a reaction vessel for a hydrothermal reaction. After the reaction, the mixture is centrifuged, washed, and dried to obtain the WO3 / Cu2WS4 composite material. This composite material is used to degrade gaseous volatile organic compounds (VOCs). The composite material prepared by this invention exhibits strong photocatalytic performance and shows great research potential and application prospects in the treatment of VOCs.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a method for preparing and applying a WO3 / Cu2WS4 composite material. Background Technology

[0002] With the continuous progress and development of society in recent years, environmental pollution problems have also emerged. Among them, the control of volatile organic pollutants (VOCs) has become a key issue in environmental protection. VOCs, such as styrene, are widely used as an effective adhesive in plastics and resin material manufacturing. Long-term exposure to styrene can cause various health problems. Therefore, developing an efficient VOCs treatment technology has become an important issue in the current management of emerging pollutants.

[0003] In recent years, photocatalysis technology has attracted widespread attention due to its advantages such as being green and energy-saving, having mild reaction conditions, and producing no secondary pollution. It is expected to become a new process for air treatment, especially for recalcitrant and non-biodegradable organic pollutants. Compared to traditional chemical treatment methods, photocatalysis is a promising green technology.

[0004] Tungsten-based semiconductors are commonly used in photocatalysis due to their resistance to photocorrosion and good chemical stability. Among them, WO3 has a band gap (Eg) of about 2.6 eV and has limited absorption of visible light.

[0005] Furthermore, the low conduction band potential and low photogenerated carrier separation efficiency limit the improvement of WO3 photocatalytic activity. Therefore, metal doping and heterojunction construction are needed to enhance the visible light photocatalytic degradation capability of the material. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying WO3 / Cu2WS4 composite material, thereby solving the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, a method for preparing a WO3 / Cu2WS4 composite material is provided, comprising the following steps: Hydrochloric acid was slowly poured into a sodium tungstate dihydrate solution and stirred to obtain a mixture. The mixture was then transferred to a reaction vessel and heated for a hydrothermal reaction. After heating was completed and the mixture was allowed to cool naturally, it was washed and dried to obtain WO3 powder. The WO3 powder was dispersed in water and ultrasonically treated to obtain a WO3 solution. Copper chloride dihydrate and sodium tungstate dihydrate were dissolved in a solvent and stirred until dissolved. Then, a sulfur source and WO3 solution were added, stirred and mixed, and then transferred to a reaction vessel for hydrothermal reaction. After the reaction, the mixture was centrifuged, washed, and dried to obtain the WO3 / Cu2WS4 composite material.

[0008] Preferably, the method for preparing sodium tungstate dihydrate solution includes: completely dissolving sodium tungstate dihydrate in water; the reaction vessel is a stainless steel high-pressure vessel with a Teflon liner.

[0009] Furthermore, the amount of sodium tungstate dihydrate added is 1-2g; the concentration and amount of hydrochloric acid added are 30-40% and 30-40ml, respectively.

[0010] Preferably, the mixing and stirring time of the sodium tungstate dihydrate solution and the hydrochloric acid solution is ≥30 minutes.

[0011] Preferably, when dispersing WO3 powder in water, the mass of WO3 powder added per milliliter of water is 0.01-0.1g, and the ultrasonic treatment time is ≥30 minutes.

[0012] Preferably, the sulfur source includes thioacetamide.

[0013] Preferably, the mass ratio of WO3 powder to Cu2WS4 is 2-6:1.

[0014] It should be noted that in the synthesis of the composite material, Cu2WS4 is generated by the reaction of copper chloride dihydrate, sodium tungstate dihydrate, and thioacetamide (TAA) under hydrothermal conditions.

[0015] According to the reaction formula 2CuCl2 2H2O + Na2WO4 The theoretical yield of Cu2WS4 can be calculated from the reaction 2H2O + 4TAA → Cu2WS4. The mass ratio of WO3 powder to Cu2WS4 is the mass ratio of the theoretical yield of WO3 powder to Cu2WS4.

[0016] The crystal plane matching and interface defect density of WO3 and Cu2WS4 directly affect the migration efficiency of photogenerated carriers. Not any oxide can form a high-quality heterojunction interface with Cu2WS4. This invention achieves close contact between the two phases through specific ratios and ultrasonic pre-dispersion.

[0017] Preferably, the solvent includes deionized water and / or ethanol; the mass of copper chloride dihydrate, sodium tungstate dihydrate, and sulfur source added per milliliter of solvent is 0.00050-0.001g, 0.00050-0.001g, and 0.001-0.002g, respectively.

[0018] Preferably, when the mixture is transferred to a reactor for hydrothermal reaction, the temperature of the reactor is set to 120-200°C, and the working time of the reactor is 10-14 hours.

[0019] Preferably, when adding sulfur source and WO3 solution, stirring and mixing, and then transferring to a reaction vessel for hydrothermal reaction, the stirring time is ≥30 minutes, the temperature of the reaction vessel is set to 150-250℃, and the working time of the reaction vessel is 70-80 hours.

[0020] It should be noted that WO3 may undergo phase transition or dissolve in high temperature, alkaline conditions, or certain solvents. This invention provides optimized conditions for the hydrothermal reaction temperature, time, and solvent system, which can ensure the structural stability of WO3 and achieve uniform loading of Cu2WS4.

[0021] Secondly, the WO3 / Cu2WS4 composite material is used to degrade gaseous volatile organic compounds, including styrene. The WO3 / Cu2WS4 composite material is prepared according to the aforementioned method for preparing the WO3 / Cu2WS4 composite material.

[0022] It should be noted that heterojunctions in existing technologies are mostly used in liquid-phase systems (such as for the degradation of tetracycline, RhB, or the reduction of Cr(VI)), while this invention targets gaseous styrene. Gas-solid phase photocatalysis places higher demands on the exposure of the catalyst's surface active sites, mass transfer efficiency, and humidity adaptability. The WO3 / Cu2WS4 composite material system prepared in this invention exhibits excellent performance in the degradation of gaseous VOCs.

[0023] The beneficial effects of this invention are as follows: Regarding the reported heterojunction systems such as Cu2WS4 / Bi2WO6 and Cu2WS4 / NiTiO3 in the prior art, this application uses WO3 to replace NiTiO3 or other oxide semiconductors. This is not a simple conventional equivalent replacement; certain technical difficulties remain in material matching and preparation. Specifically, these difficulties manifest in the following aspects: Firstly, WO3 and Cu2WS4 differ significantly in band structure, conduction / valence band positions, and conductivity type, leading to uncertainty in the heterojunction type and charge transport path. Secondly, their crystal structures and surface properties differ considerably, making interface construction difficult and easily introducing defects that affect performance. Furthermore, in hydrothermal / solvothermal systems containing sulfur precursors, WO3 may undergo local sulfidation or generate impurity phases, increasing the complexity of preparation. Therefore, the construction of WO3 / Cu2WS4 heterojunctions presents certain technical challenges in terms of band matching, interface regulation, and reaction condition control.

[0024] The WO3 / Cu2WS4 photocatalytic composite material prepared in this invention exhibits high photocatalytic activity, a wide light absorption range, and a small band gap. It reacts with volatile organic compounds (VOCs) under mild conditions with high degradation efficiency, and can catalyze the degradation of VOCs even under sunlight. Establishing a photocatalytic system using the WO3 / Cu2WS4 photocatalytic composite material provides a novel approach for the degradation of VOCs. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 The scanning electron microscope (SEM) spectrum of the WO3 / Cu2WS4 composite material prepared in this invention; Figure 2 The X-ray diffraction (XRD) spectrum of the WO3 / Cu2WS4 composite material prepared in this invention; Figure 3 The image shows the photocatalytic degradation of styrene by the WO3 / Cu2WS4 composite material prepared in this invention. Figure 4 The graph shows the photocatalytic degradation of styrene by different dosages of the WO3 / Cu2WS4 composite material prepared in this invention; Figure 5 The image shows the photocatalytic degradation of WO3 / Cu2WS4 composite material prepared in this invention for different styrene concentrations. Figure 6 The graph shows the photocatalytic degradation of styrene by WO3 / Cu2WS4 composite materials with different ratios prepared in this invention. Figure 7 The X-ray photoelectron (XPS) spectrum of the WO3 / Cu2WS4 composite material prepared in this invention; Figure 8 This is a mechanism diagram of the WO3 / Cu2WS4 composite material prepared in this invention. Detailed Implementation

[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0027] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0028] Unless otherwise specified, the equipment and materials used in the embodiments can be readily obtained from commercial companies.

[0029] Example 1 A method for preparing a WO3 / Cu2WS4 composite material, the specific steps of which are as follows: First, prepare WO3 powder: Tungsten trioxide (WO3) is prepared using a hydrothermal method. 1.15g of sodium tungstate dihydrate (Na2WO4) is added... Add 2H₂O to 35 mL of distilled water, then slowly add 35 mL of 35% hydrochloric acid (HCl) under continuous stirring, and stir the mixture for 30 minutes to obtain a homogeneous yellow liquid, i.e., the mixture. Transfer the obtained mixture to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, and hydrothermally react at 160 °C for 12 hours. Wash the product several times with water and anhydrous ethanol, and dry the product to obtain a yellow WO₃ powder.

[0030] Next, a mixed solution was prepared: 0.2 g of WO3 powder was dispersed in 30 mL of deionized water and sonicated for 30 minutes to obtain a WO3 solution.

[0031] Preparation of composite material: 39 mg of copper chloride dihydrate (CuCl2) was added. 2H2O) and 38mg sodium tungstate dihydrate (Na2WO4) Dissolve 2H₂O in a mixed solution consisting of 25 mL of deionized water and 25 mL of ethanol. Stir the mixture magnetically for 20 min to form a homogeneous solution.

[0032] Subsequently, 80 mg of thioacetamide (TAA) was added as a sulfur source, along with WO3 solution, and stirring continued for 30 min. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to hydrothermal reaction at 200 °C for 72 h. After natural cooling to room temperature, the precipitate was collected by centrifugation and washed three times with deionized water and anhydrous ethanol to remove residual ions and unreacted substances. Finally, it was dried under vacuum at 60 °C for 10 h to obtain the WO3 / Cu2WS4 composite material.

[0033] Images of WO3 / Cu2WS4 nanocomposites in SEM (Self-Electron Microscopy) are shown below. Figure 1 As shown.

[0034] Depend on Figure 2 As can be seen, the XRD patterns of the WO3 / Cu2WS4 photocatalytic material show characteristic peaks of WO3 and Cu2WS4, without excessive impurities, proving that the composite material was successfully synthesized.

[0035] The WO3 / Cu2WS4 photocatalytic material prepared above was subjected to photocatalytic experiments: The photocatalytic activity of the WO3 / Cu2WS4 catalyst was evaluated by degrading gaseous styrene under visible light irradiation (λ>400nm). A 300W UV-Vis lamp was used as the light source.

[0036] The photocatalytic degradation of gaseous styrene was conducted in a 300 mL reactor at room temperature (25℃±2℃). The reactor was positioned axially and contained within a visible light box. The light was placed in a dark box approximately 100 mm from the top of the reactor, and a filter with a wavelength greater than 400 nm was used to obtain visible light. Gas samples were extracted every 15 minutes, and the styrene concentration within the reactor was determined by gas chromatography.

[0037] The formula for the degradation rate of styrene is as follows: η = [(C0-C) / C0] × 100% In the formula: η is the styrene degradation rate; C is the concentration of styrene after degradation; C0 is the concentration of styrene before degradation.

[0038] Depend on Figure 3 As observed, WO3, Cu2WS4, and the WO3 / Cu2WS4 photocatalytic material prepared in Example 1 were used to degrade styrene. The WO3 / Cu2WS4 photocatalytic material achieved a styrene degradation rate of 97.3% after 120 min of reaction, while the degradation rates of WO3 and Cu2WS4 were approximately 81.1% and 81.4%, respectively, after 120 min of reaction. This demonstrates the superior degradation effect of the WO3 / Cu2WS4 photocatalytic system on styrene.

[0039] To understand the effect of WO3 / Cu2WS4 photocatalyst dosage on the photocatalytic degradation of styrene, 25 mg, 50 mg, 75 mg, and 100 mg of the composite catalyst (WO3 / Cu2WS4) were added at a concentration of 200 mg / m³. 3 The degradation effect of the catalyst was observed in a styrene reactor. (See...) Figure 4 As shown, within a certain range, the more composite catalyst is added, the better the photocatalytic effect; however, as the amount of catalyst added increases, the degradation effect reaches saturation and there is no significant change.

[0040] To understand the effect of different styrene concentrations on photocatalytic degradation, four groups of different concentrations (100 mg / m³) were used. 3 200mg / m 3 300mg / m 3 500mg / m 3 A comparative analysis of the degradation of styrene was conducted, from... Figure 5 It can be seen that the WO3 / Cu2WS4 composite material at low and medium concentrations (≤300mg / m³) exhibits good performance. 3It exhibits excellent degradation efficiency under visible light irradiation, with a removal rate exceeding 90% after 90 minutes of visible light exposure. Even at 500 mg / m³... 3 Even at high initial concentrations, the catalyst still achieves a significant degradation efficiency of 86.9%, indicating that it has a strong ability to treat high concentrations of volatile organic pollutants (VOCs) under normal temperature and pressure conditions.

[0041] Example 2 By adjusting the amount of WO3 added, various composite materials with different ratios were synthesized. They were labeled as WO3 / CWS-x, where x represents the mass of Cu2WS4 in the composite material (x=40%, 30%, 20%).

[0042] Referring to the method of Example 1, (1) when x=40%, 75mg of WO3 powder was dispersed in 30mL of deionized water and sonicated for 30 minutes to obtain a WO3 solution. The remaining steps were the same as in Example 1. (2) when x=30%, 117mg of WO3 powder was dispersed in 30mL of deionized water and sonicated for 30 minutes to obtain a WO3 solution. The remaining steps were the same as in Example 1. (3) when x=20%, all steps were the same as in Example 1.

[0043] Based on the photocatalytic materials with different ratios prepared above, the same photocatalytic experiments as in Example 1 were conducted: Depend on Figure 6 As can be seen, the composite materials with different ratios all exhibit good photocatalytic performance, among which WO3 / CWS-20 is the best.

[0044] Example 3 XPS results confirmed the successful fabrication of the WO3 / Cu2WS4 heterojunction. In the high-resolution spectrum, the W4f peak located at approximately 35-38 eV was attributed to W. 6+ The species confirms the existence of WO3. The Cu 2p spectrum shows Cu... + The characteristic peaks, accompanied by weak satellite peaks, indicate the presence of Cu in the system. + / Cu 2+ Coexistence. The S 2p map is based on S 2- The dominant signal confirmed the formation of Cu2WS4. Simultaneously, the O1s spectrum showed peak fitting to identify lattice oxygen and surface-adsorbed oxygen. These results indicate that WO3 and Cu2WS4 have successfully recombinated and exhibit interfacial electronic interactions, which facilitates the separation of photogenerated carriers and thus enhances photocatalytic performance.

[0045] Example 4 To better explain the formation mechanism of WO3 / Cu2WS4 heterojunction, such as Figure 8 As shown, the photocatalytic mechanism of the present invention is as follows: The band gap of n-type semiconductor WO3 is 2.58 eV, and that of p-type semiconductor Cu2WS4 is 2.30 eV. When WO3 and Cu2WS4 form a heterojunction, an internal electric field is generated at the interface, and the conduction band potential of WO3 and the valence band potential of Cu2WS4 both satisfy the redox potential. When exposed to visible light, WO3 and Cu2WS4 generate photogenerated electrons and holes under visible light excitation, which then separate. The photogenerated electrons transfer from the conduction band of WO3 to the valence band of Cu2WS4 and recombine with the photogenerated holes, thereby reducing recombination. This electron transfer path forms a unique Z-shaped heterojunction, enhancing the separation efficiency of photogenerated carriers. The retained photogenerated electrons and holes generate superoxide radicals and hydroxyl radicals, respectively, which, together with other reactive radicals, degrade styrene.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a WO3 / Cu2WS4 composite material, characterized in that, Includes the following steps: Hydrochloric acid was slowly poured into a sodium tungstate dihydrate solution and stirred to obtain a mixture. The mixture was then transferred to a reaction vessel and heated for a hydrothermal reaction. After heating was completed and the mixture was allowed to cool naturally, it was washed and dried to obtain WO3 powder. The WO3 powder was dispersed in water and ultrasonically treated to obtain a WO3 solution. Copper chloride dihydrate and sodium tungstate dihydrate were dissolved in a solvent and stirred until dissolved. Then, a sulfur source and WO3 solution were added, stirred and mixed, and then transferred to a reaction vessel for hydrothermal reaction. After the reaction, the mixture was centrifuged, washed, and dried to obtain the WO3 / Cu2WS4 composite material.

2. The method for preparing WO3 / Cu2WS4 composite material according to claim 1, characterized in that, The preparation method of sodium tungstate dihydrate solution includes: completely dissolving sodium tungstate dihydrate in water; the reaction vessel is a stainless steel high-pressure vessel with a Teflon lining.

3. The method for preparing WO3 / Cu2WS4 composite material according to claim 2, characterized in that, The amount of sodium tungstate dihydrate added is 1-2g; the concentration and amount of hydrochloric acid added are 30-40% and 30-40ml, respectively.

4. The method for preparing a WO3 / Cu2WS4 composite material according to claim 1, characterized in that, The sodium tungstate dihydrate solution and hydrochloric acid solution are mixed and stirred for ≥30 minutes.

5. The method for preparing a WO3 / Cu2WS4 composite material according to claim 1, characterized in that, When dispersing WO3 powder in water, the mass of WO3 powder added per milliliter of water is 0.01-0.2g, and the ultrasonic treatment time is ≥30 minutes.

6. The method for preparing a WO3 / Cu2WS4 composite material according to claim 1, characterized in that, The sulfur source includes thioacetamide; the mass ratio of WO3 powder to Cu2WS4 is 2-6:

1.

7. The method for preparing a WO3 / Cu2WS4 composite material according to claim 1, characterized in that, The solvents include deionized water and / or ethanol; the mass of copper chloride dihydrate, sodium tungstate dihydrate, and sulfur source added per milliliter of solvent is 0.00050-0.001 g, 0.00050-0.001 g, and 0.001-0.002 g, respectively.

8. The method for preparing a WO3 / Cu2WS4 composite material according to claim 1, characterized in that, When the mixture is transferred to a reactor for hydrothermal reaction, the temperature of the reactor is set to 120-200℃, and the reactor operates for 10-14 hours.

9. The method for preparing a WO3 / Cu2WS4 composite material according to claim 1, characterized in that, When adding sulfur source and WO3 solution, stirring and mixing, and then transferring to a reaction vessel for hydrothermal reaction, the stirring time is ≥30 minutes, the temperature of the reaction vessel is set to 150-250℃, and the working time of the reaction vessel is 70-80 hours.

10. A WO3 / Cu2WS4 composite material used for degrading gaseous volatile organic compounds, characterized in that, The gaseous volatile organic compounds include styrene, and the WO3 / Cu2WS4 composite material is prepared according to any one of claims 1-9 by a method for preparing the WO3 / Cu2WS4 composite material.

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