A hollow composite microsphere photocatalyst containing dual promoters and its preparation method and application

Abstract

The present invention relates to a hollow composite microsphere photocatalyst MnO containing dual promoters. x The preparation method of @TiO2@WO3@Au uses SiO2 microspheres as templates and sequentially coats MnO x and TiO2, and then the SiO2 template is etched to obtain a hollow MnO x @TiO2 microspheres, then coated with WO3, and finally photoreduction deposited Au nanoparticles to simply and pollution-free prepare hollow composite microspheres containing dual promoters MnO x @TiO2@WO3@Au. Prepared MnO x The size of the @TiO2@WO3@Au hollow composite microspheres is about 300 nanometers, showing a nanoscale hollow structure. Since the light absorption of WO3 (<450 nm) and the surface plasmon resonance absorption of Au nanoparticles (450‑600 nm) do not overlap, the hollow composite microspheres MnO x @TiO2@WO3@Au can absorb ultraviolet light and most visible light, effectively broadening its light absorption range; the dual co-catalyst (MnO x The heterostructure with energy-level matching between Au and TiO2@WO3 promotes the transfer of photogenerated electrons and holes in opposite directions, improving the separation efficiency of photogenerated charges.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and specifically relates to a hollow composite microsphere photocatalyst (MnO x @TiO2@WO3@Au) and its preparation method and photocatalytic performance application research. The photocatalytic composite material can be used for photocatalytic degradation of phenol under xenon lamp light. Background Art

[0002] Phenol is widely used in industries such as petrochemicals, textiles, and plastic manufacturing, and is one of the main pollutants discharged into industrial wastewater. Phenol pollutants are highly toxic, bioaccumulative, and difficult to degrade naturally. The main methods for treating phenol-containing wastewater are adsorption, biodegradation, and photocatalysis. Among them, the adsorption method has high regeneration costs; the biodegradation method has poor degradation effects due to the self-inhibition of phenol on organisms; and the photocatalytic method has attracted much attention due to its advantages such as rapid decomposition, thorough treatment, and no secondary pollution. The core of photocatalytic technology is the semiconductor-based photocatalytic process, that is, the redox process driven by sunlight. Therefore, the construction of efficient semiconductor photocatalysts is the key to realizing photocatalytic technology.

[0003] Among many semiconductor photocatalytic materials, TiO2 has attracted much attention due to its advantages such as non-toxicity, low price and stability. However, due to its large band gap (3.0-3.2 eV) and narrow spectral response region, TiO2 can only utilize ultraviolet light that does not exceed 5% of the total solar energy. In addition, photogenerated electrons and holes in pure TiO2 are prone to rapid recombination. Therefore, the light absorption capacity of TiO2 and the separation efficiency of photogenerated charges are the main factors limiting its photocatalytic performance.

[0004] In order to solve the existing problems of TiO2 and improve its photocatalytic performance, this application will construct TiO2@WO3 heterojunction hollow nanospheres and introduce MnO x In this structure, TiO2 can absorb ultraviolet light, WO3 absorbs visible light, and the surface plasmon resonance absorption of the introduced Au nanoparticles (450-600 nm) does not overlap with the light absorption of WO3 (<450 nm), which can achieve triple absorption of sunlight. The introduced dual co-catalysts and heterojunction promote the transfer of photogenerated carriers in opposite directions, further improving the photocatalytic activity of TiO2. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a hollow composite microsphere photocatalyst MnO containing dual promoters. x@TiO2@WO3@Au. The photocatalyst has a nanoscale hollow layered structure, which can absorb ultraviolet light and most visible light, effectively broadening its light absorption range. The introduced dual co-catalysts and heterojunctions promote the effective separation of photogenerated carriers and improve the activity of the photocatalyst, and can be used for photocatalytic degradation of phenol.

[0006] The present invention also provides the hollow composite microsphere photocatalyst MnO containing dual promoters. x The preparation method of @TiO2@WO3@Au and its application in photocatalytic degradation of phenol under visible light. The preparation method is simple, easy to operate, low in cost, and environmentally friendly, and the photocatalytic degradation effect of phenol under xenon light is good.

[0007] To achieve the above purpose, the present invention adopts the following technical solution.

[0008] The present invention provides a hollow composite microsphere photocatalyst containing a spatially separated dual promoter, wherein the photocatalyst is a TiO2@WO3 hollow composite microsphere with an oxidation promoter MnO2 on its inner and outer surfaces. x and reduction co-catalyst Au; the photocatalyst is a hollow core-shell structure constructed by a layer-by-layer coating method.

[0009] The present invention discloses a method for preparing a hollow composite microsphere photocatalyst containing dual promoters, which comprises the following steps:

[0010] 1) Hollow MnO x @TiO2 nanospheres are dispersed in deionized water, and then ethylene glycol is added to disperse them evenly;

[0011] 2) Add Na2WO4•2H2O to the mixed solution obtained in step 1), and then place in a 60-85°C water bath and stir for 10-50 minutes;

[0012] 3) Add hydrochloric acid to the mixed solution of step 2), stir and react for 1-4 hours, centrifuge, wash and dry, and then heat treat at 500-700℃ for 2-5 hours to obtain MnO x @TiO2@WO3 microspheres;

[0013] 4) The product MnO obtained in step 3) x The @TiO2@WO3 microspheres were dispersed in deionized water, and then HAuCl4·4H2O aqueous solution was added. After irradiation for 1-4 min under a 200-400W xenon lamp light source system with stirring, the product was collected by centrifugation, washed and dried to obtain the photocatalyst material MnO x @TiO2@WO3@Au.

[0014] Specifically, in step 1), the hollow MnO xThe mass ratio of TiO2 nanospheres to deionized water is 1:1000-1200, hollow MnO x @The mass ratio of TiO2 nanospheres to ethylene glycol is 1:30-50.

[0015] Further, in step 2), the Na2WO4•2H2O and the hollow MnO x @The molar ratio of TiO2 nanospheres is 0.5-2:10.

[0016] Specifically, in step 3), the molar concentration of the added hydrochloric acid is 0.4-0.6 mol / L, and the mass ratio of hydrochloric acid to Na2WO4•2H2O is 1000:1-3.

[0017] Further, in step 4), the MnO x The mass ratio of @TiO2@WO3 microspheres to deionized water is 1-3:1000, and the mass ratio of HAuCl4·4H2O to MnO x The mass ratio of @TiO2@WO3 microspheres is 1-3:20.

[0018] Specifically, in step 1), the hollow MnO x Preparation method of @TiO2 nanoparticles based on SiO2@MnO x Using nanospheres as substrate, a uniform porous TiO2 shell core-shell structure was prepared by a variety of kinetically controlled coating methods. The preparation was carried out by the following steps:

[0019] 0.1-0.3g SiO2@MnO x The nano-microspheres are dispersed in anhydrous ethanol and mixed with 0.1-1 ml of concentrated ammonia water (25-28 wt%) under ultrasonic action for 10-20 min, then 0.5-1 ml of tetrabutyl titanate is added, and the reaction is continuously carried out under a constant temperature water bath of 40-50°C with mechanical stirring for 20-30 h, the product is separated and collected, washed, and treated with a NaOH solution with a molar concentration of 1-3 mol / L at room temperature for 4-6 h, centrifuged, washed, and dried to obtain the product.

[0020] Furthermore, the SiO2@MnO x Preparation method of nano-microspheres: SiO2 microspheres synthesized by tetraethyl orthosilicate as silicon source were used as core materials, and SiO2@MnO nanospheres with uniform growth and good dispersion were prepared by hydrothermal method. x The nanospheres are prepared by the following steps:

[0021] Ultrasonic disperse the SiO2 template in deionized water (the mass ratio of SiO2 template to deionized water can be 1:200-400), then add KMnO4, the mass ratio of KMnO4 to SiO2 template is 1:3-5, stir for 20-40 minutes, transfer to a high-pressure reactor and react at 100-200°C for 4-10 hours. After the reaction is completed, cool to room temperature, separate and collect the product, wash and dry to obtain.

[0022] Specifically, the SiO2 template is prepared by the following steps: dispersing tetraethyl orthosilicate in anhydrous ethanol, adding concentrated ammonia water (25-28 wt%) and deionized water under stirring at room temperature and continuously stirring for 20-30 hours, and after the reaction is completed, centrifuging, washing and drying to obtain the SiO2 template; the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 1:30-60; the mass ratio of tetraethyl orthosilicate to concentrated ammonia water and deionized water is 1:4-6:1-3.

[0023] The invention provides a hollow composite microsphere photocatalyst containing double promoters prepared by the preparation method.

[0024] The present invention also provides the use of the hollow composite microsphere photocatalyst containing dual promoters in the visible light catalytic degradation of phenol.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] Hollow composite microsphere photocatalyst MnO containing dual promoters of the present invention x The preparation process of @TiO2@WO3@Au uses SiO2 as a template and coats MnO x and TiO2, and then the SiO2 template is etched to obtain a hollow MnO x @TiO2 microspheres, then coated with WO3, and finally photoreduced and deposited Au nanoparticles to simply and non-pollutingly prepare the dual-promoter-loaded MnO x @TiO2@WO3@Au composite microspheres. Prepared MnO x The size of @TiO2@WO3@Au hollow composite microspheres is about 300 nanometers, with a hollow structure that can absorb ultraviolet light and most visible light, effectively broadening its light absorption range; the dual co-catalyst (MnO x The heterostructure with energy-level matching between Au and TiO2@WO3 promotes the transfer of photogenerated electrons and holes in opposite directions, improves the separation efficiency of photogenerated charges, and has good phenol degradation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 MnO described in Example 1 xSchematic diagram of the preparation process of @TiO2@WO3@Au hollow composite microspheres;

[0028] Figure 2 The MnO prepared in Example 1 x SEM photo of @TiO2@WO3@Au hollow composite microspheres, and the inset is its TEM photo;

[0029] Figure 3 This is a scanning electron microscope photo of the TiO2@WO3 hollow composite microspheres prepared in Comparative Example 1;

[0030] Figure 4 MnO prepared in Comparative Example 2 x SEM photo of @TiO2@WO3 hollow composite microspheres;

[0031] Figure 5 This is a scanning electron microscope photo of the TiO2@WO3@Au hollow composite microspheres prepared in Comparative Example 3;

[0032] Figure 6 TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 x @TiO2@WO3, TiO2@WO3@Au, MnO x X-ray diffraction pattern of @TiO2@WO3@Au hollow composite microspheres;

[0033] Figure 7 The MnO prepared in Example 1 x X-ray photoelectron spectroscopy of @TiO2@WO3@Au hollow composite microspheres;

[0034] Figure 8 TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 x @TiO2@WO3, TiO2@WO3@Au, MnO x Photocatalytic degradation performance of phenol by @TiO2@WO3@Au hollow composite microspheres;

[0035] Fig. 9 The MnO prepared in Example 1 x @TiO2@WO3@Au hollow composite microspheres cycle test results;

[0036] Fig.10 TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 x @TiO2@WO3, TiO2@WO3@Au, MnO x UV-visible absorption spectrum of @TiO2@WO3@Au hollow composite microspheres;

[0037] Fig.11 The TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 are given. x @TiO2@WO3, TiO2@WO3@Au, MnO x Fluorescence spectrum of @TiO2@WO3@Au hollow composite microspheres;

[0038] Fig.12 The TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 are given respectively. x @TiO2@WO3, TiO2@WO3@Au, MnO x Surface photovoltage spectrum of @TiO2@WO3@Au hollow composite microspheres. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0040] In the following examples, the raw materials used, unless otherwise specified, are common commercial products that can be directly purchased or can be prepared by conventional methods in the art.

[0041] In the present invention, unless otherwise specified, the stirring is magnetic stirring, and the stirring speed is 150-600 rpm. Room temperature refers to 25±5°C.

[0042] Example 1

[0043] A hollow composite microsphere photocatalyst MnO containing dual promoters x Preparation method of @TiO2@WO3@Au (see the preparation diagram Figure 1 ), which specifically includes the following steps:

[0044] 1) Hollow MnO x @TiO2 nanospheres were ultrasonically dispersed in deionized water, and then ethylene glycol was added to disperse them evenly; hollow MnO x The mass ratio of TiO2 nanospheres to deionized water is 1:1000; hollow MnO x @The mass ratio of TiO2 nanospheres to ethylene glycol is 1:40;

[0045] 2) Add Na2WO4•2H2O (Na2WO4•2H2O and hollow MnO x @The molar ratio of TiO2 nanospheres is 1:10); then the mixture is placed in a 75℃ water bath and stirred at constant temperature for 30 minutes;

[0046] 3) Add 0.5 mol / L hydrochloric acid (the mass ratio of hydrochloric acid to Na2WO4•2H2O is 1000:1) to the constant temperature reaction solution in step 2); stir and react for 2 hours, centrifuge, wash three times with water and ethanol respectively, dry at 60°C for 8 hours, and heat treat the product at 600°C for 3 hours to obtain MnO x @TiO2@WO3 microspheres;

[0047] 4) The product MnO obtained in step 3) x @TiO2@WO3 microspheres were ultrasonically dispersed in deionized water (MnO x @TiO2@WO3 microspheres and deionized water in a mass ratio of 1:1000), and then HAuCl4·4H2O aqueous solution (0.4 g / L) was added. HAuCl4·4H2O and MnO x The mass ratio of @TiO2@WO3 microspheres was 1:10 and stirred for 5 min. After irradiation under a 300W xenon light source system for 2 min, the obtained product was centrifuged and collected, washed with deionized water and ethanol for 3 times respectively, and then dried in a constant temperature drying oven at 60°C for 8 h to obtain the photocatalyst material MnO x @TiO2@WO3@Au.

[0048] The hollow MnO x @TiO2 nanospheres were prepared by the following steps: ① 0.2g SiO2@MnO x Nanospheres dispersed in anhydrous ethanol (SiO2@MnO x The mass ratio of nanospheres to anhydrous ethanol is 1:2500), and mixed with 0.5 mL of concentrated ammonia (25-28 wt%) for 15 min under ultrasonic action; ② 0.75 mL of tetrabutyl titanate was added dropwise to the mixed solution in step ①, and the reaction was continuously mechanically stirred for 24 h under a constant temperature water bath at 45°C. After the reaction, the obtained products were separated and collected, and washed with deionized water and ethanol 3 times each. ③ The product obtained in step ② was treated with a NaOH solution with a molar concentration of 2 mol / L at room temperature for 5 h, centrifuged, washed with water and ethanol 3 times respectively, and dried at 60°C for 8 h.

[0049] The SiO2@MnO xThe nanospheres were prepared by the following steps: ① ultrasonically disperse the SiO2 template in deionized water (the mass ratio of SiO2 template to deionized water was 1:300); ② add KMnO4 (the mass ratio of KMnO4 to SiO2 template was 1:4) to the mixed solution in step ① and stir for 30 minutes. Then transfer to a high-pressure reactor and react at 150°C for 6 hours. After the reaction is completed, cool to room temperature, separate and collect the obtained products, wash them with deionized water and ethanol three times respectively, and then dry the obtained powder at 80°C overnight to obtain the obtained product.

[0050] The preparation method of the SiO2 template comprises the following steps: ① dispersing tetraethyl orthosilicate in anhydrous ethanol and stirring continuously for 15 min at room temperature, wherein the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 1:30; ② continuously adding concentrated ammonia water (25-28wt%) and deionized water to the mixed solution in step ① and stirring continuously for 24h, wherein the mass ratio of tetraethyl orthosilicate to concentrated ammonia water and deionized water is 1:5:2. After the reaction is completed, centrifugation is performed, and water and ethanol are respectively washed 3 times, and dried at 60°C for 8h to obtain the template.

[0051] Figure 2 The MnO prepared in Example 1 is given. x SEM and TEM images of @TiO2@WO3@Au hollow composite microspheres (inset); Figure 2 It can be seen that the prepared MnO x The diameter of the @TiO2@WO3@Au composite microspheres is about 300 nm, and the surface is uneven. As can be seen from the illustration, the nanospheres are hollow structures, and there are dispersed Au nanoparticles on the surface of the microspheres, with particle sizes ranging from 5nm to 15nm.

[0052] Comparative Example 1

[0053] A method for preparing a core-shell structured TiO2@WO3 ultraviolet / visible light catalyst (TiO2@WO3 hollow composite microspheres) comprises the following steps:

[0054] 1) Ultrasonic dispersion of hollow TiO2 nanospheres in deionized water (the mass ratio of hollow TiO2 nanospheres to deionized water is 1:1000), and then adding ethylene glycol (the mass ratio of hollow TiO2 nanospheres to ethylene glycol is 1:40), and ultrasonic dispersion is uniform;

[0055] 2) Add Na2WO4•2H2O (the molar ratio of W to Ti is 8%) to the mixed solution obtained in step 1); and place the mixed solution in a 75°C water bath and stir at a constant temperature for 30 minutes;

[0056] 3) Add hydrochloric acid with a molar concentration of 0.5 mol / L (the mass ratio of hydrochloric acid to Na2WO4•2H2O is 1000:1) to the constant temperature reaction solution in step 2); stir the reaction for 2 hours, centrifuge, wash with water and ethanol three times respectively, dry at 60°C for 8 hours, and heat treat the product at 600°C for 3 hours.

[0057] The preparation method of hollow TiO2 nanospheres uses SiO2 microspheres synthesized with tetraethyl orthosilicate as a silicon source as a core material, and adopts a variety of kinetically controlled coating methods to prepare a uniform porous TiO2 shell core-shell structure. Specifically, the following steps are included: ① The SiO2 template is dispersed in anhydrous ethanol (the mass ratio of SiO2 template to anhydrous ethanol is 1:2500), and mixed with 0.5ml of concentrated ammonia water for 15 min under ultrasonic action; ② 0.75mL of tetrabutyl titanate is added dropwise to the mixed solution in step ①, and the reaction is continuously mechanically stirred for 24 hours under a constant temperature water bath of 45°C. The obtained products are separated and collected, and washed with deionized water and ethanol for 3 times respectively. Then the obtained powder is dried at 80°C overnight. ③ The product obtained in step ② is treated with a NaOH solution with a molar concentration of 1 mol / L at room temperature for 5 hours. Centrifugal separation, water and ethanol are washed 3 times respectively, and dried at 60°C for 8 hours to obtain hollow TiO2 nanospheres.

[0058] The preparation method of the SiO2 template is shown in Example 1.

[0059] Figure 3 The scanning electron microscope photo of the TiO2@WO3 hollow composite microspheres prepared in Comparative Example 1 is given; Figure 3 It can be seen that the diameter of the prepared TiO2@WO3 composite microspheres is about 300 nm, the nano-microspheres are hollow and have an uneven surface.

[0060] Comparative Example 2

[0061] A Mn-loaded TiO2@WO3 photocatalyst (MnO x The preparation method of @TiO2@WO3 hollow composite microspheres comprises the following steps:

[0062] 1) Hollow MnO x @TiO2 nanospheres were ultrasonically dispersed in deionized water, and then ethylene glycol was added to disperse them evenly; hollow MnO x The mass ratio of TiO2 nanospheres to deionized water is 1:1000; hollow MnO x @The mass ratio of TiO2 nanospheres to ethylene glycol is 1:40;

[0063] 2) Add Na2WO4•2H2O (Na2WO4•2H2O and hollow MnOx @The molar ratio of TiO2 nanospheres is 1:10); and the mixed solution is placed in a 75℃ water bath and stirred at constant temperature for 30 minutes;

[0064] 3) Add hydrochloric acid with a molar concentration of 0.5 mol / L (the mass ratio of hydrochloric acid to Na2WO4•2H2O is 1000:1) to the constant temperature reaction solution in step 2); stir the reaction for 2 hours, centrifuge, wash with water and ethanol three times respectively, dry at 60°C for 8 hours, and heat treat the product at 600°C for 3 hours.

[0065] The hollow MnO x The preparation method of @TiO2 nanospheres is as described in Example 1. The SiO2@MnO x The preparation methods of nano-microspheres and SiO2 templates are all based on Example 1.

[0066] Figure 4 The MnO prepared in Comparative Example 2 is given. x SEM photo of @TiO2@WO3 hollow composite microspheres; Figure 4 It can be seen that the prepared MnO x The diameter of @TiO2@WO3 composite microspheres is about 300 nm. The nano-microspheres are hollow and have an uneven surface. x On the inner surface of hollow microsphere TiO2@WO3, the hollow microsphere MnO x There is no obvious difference in the surface morphology of the TiO2@WO3 hollow microspheres obtained in Example 1.

[0067] Comparative Example 3

[0068] A method for preparing Au-loaded TiO2@WO3 photocatalyst (TiO2@WO3@Au hollow composite microspheres) comprises the following steps:

[0069] The hollow TiO2@WO3 nanospheres were ultrasonically dispersed in deionized water (the mass ratio of hollow TiO2@WO3 nanospheres to deionized water was 1:1000); then HAuCl4·4H2O aqueous solution was added and stirred for 5 minutes, and the mass ratio of HAuCl4·4H2O to TiO2@WO3 nanospheres was 1:10. After irradiation for 2 minutes under a 300W xenon light source system, the product was centrifuged and collected, and washed with deionized water and ethanol for 3 times respectively. Then it was dried in a constant temperature drying oven at 60°C for 8 hours to obtain the photocatalyst material TiO2@WO3@Au.

[0070] The hollow TiO2@WO3 nanospheres are prepared by the following steps: ① ultrasonically dispersing the hollow TiO2 nanospheres in deionized water, wherein the mass ratio of the hollow TiO2 nanospheres to the deionized water is 1:1000; then adding ethylene glycol, wherein the mass ratio of the hollow TiO2 nanospheres to the ethylene glycol is 1:40, and ultrasonically dispersing the mixture uniformly; ② adding Na2WO4•2H2O (the molar ratio of W to Ti is 8%) to the mixed solution obtained in step ①; and placing the mixed solution at 75 ℃ water bath and stir at constant temperature for 30 minutes; ③ add hydrochloric acid with a molar concentration of 0.5 mol / L (the mass ratio of hydrochloric acid to Na2WO4•2H2O is 1000:1) to the constant temperature reaction solution in step ②; after stirring for 2 hours, centrifuge and wash with water and ethanol for 3 times respectively, dry at 60℃ for 8 hours, and heat treat the product at 600℃ for 3 hours to obtain hollow TiO2@WO3 nanospheres, also referred to as hollow structure TiO2@WO3 UV / visible light catalysts in this application.

[0071] The preparation method of hollow TiO2 nano-microspheres uses SiO2 microspheres synthesized with tetraethyl orthosilicate as a silicon source as a core material, and adopts a variety of kinetically controlled coating methods to prepare a uniform porous TiO2 shell core-shell structure. Specifically, the following steps are included: ① The SiO2 template is dispersed in anhydrous ethanol (the mass ratio of SiO2 template to anhydrous ethanol is 1:2500), and mixed with 0.5ml of concentrated ammonia water for 15 min under ultrasonic action; ② 0.75mL of tetrabutyl titanate is added dropwise to the mixed solution in step ①, and the reaction is continuously mechanically stirred for 24 hours under a constant temperature water bath of 45°C. The obtained products are separated and collected, and washed with deionized water and ethanol for 3 times respectively. Then the obtained powder is dried at 80°C overnight. ③ The product obtained in step ② is treated with a NaOH solution with a molar concentration of 1 mol / L at room temperature for 5 hours. Centrifugal separation, water and ethanol are washed 3 times respectively, and dried at 60°C for 8 hours to obtain hollow TiO2 nano-microspheres.

[0072] The preparation method of the SiO2 template is shown in Example 1.

[0073] Figure 5 The scanning electron microscope photo of the TiO2@WO3@Au hollow composite microspheres prepared in Comparative Example 3 is given; Figure 5 It can be seen that the diameter of the prepared TiO2@WO3@Au composite microspheres is about 300 nm. The nanospheres are hollow and have an uneven surface. Since the Au nanoparticles are very small, they cannot be seen in this figure.

[0074] Figure 6 The TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 are given. x @TiO2@WO3, TiO2@WO3@Au, MnO xX-ray diffraction pattern of @TiO2@WO3@Au hollow composite microspheres; Figure 6 It can be seen that compared with the XRD spectrum of pure TiO2, the MnO x The typical diffraction peaks of @TiO2@WO3@Au hollow composite microspheres correspond to MnO x , anatase TiO2 and monoclinic WO3. Due to the low gold content, no gold diffraction peak was observed. x The XRD spectra of @TiO2@WO3 and TiO2@WO3@Au respectively showed typical diffraction peaks of the corresponding metal oxides, proving that the samples of Comparative Examples 1-3 were obtained.

[0075] In order to prove that the MnO prepared in Example 1 x @TiO2@WO3@Au sample contains Au, Figure 7 Given MnO x XPS spectrum of @TiO2@WO3@Au hollow composite microspheres; Figure 7 It can be seen that: MnO x The Au element appeared in the @TiO2@WO3@Au sample, which is consistent with Figure 2 The TEM results in the illustration are consistent. Since XPS can only detect a few nanometers in thickness, the Mn element was not detected, but XRD has proved that MnO x existence.

[0076] Catalyst degradation test

[0077] Weigh 50 mg of TiO2@WO3, MnO x @TiO2@WO3, TiO2@WO3@Au, MnO x The @TiO2@WO3@Au composite catalyst was added to 50 ml of 10 mg / L phenol solution, placed in the dark and stirred for 30 minutes to reach equilibrium, and then photocatalytic reaction was carried out under a xenon lamp (300W) light source system. Samples were taken every 10 minutes for a total of 100 minutes. After filtration, the concentration of phenol in the supernatant was determined by high performance liquid chromatography. The chromatographic column was C18 (length 250 mm, inner diameter 4 mm), and the eluent: methanol and water ratio was 60%:40% (volume ratio). The phenol degradation results of different catalysts are shown in Figure 2. Figure 8 As shown, from Figure 8 It can be seen that the TiO2@WO3, MnO x @TiO2@WO3, TiO2@WO3@Au, MnO x@TiO2@WO3@Au photocatalysts have a good degradation effect on phenol. Composite catalyst MnO x @TiO2@WO3@Au can degrade 98% of phenol within 100 min, with the best degradation effect, which is better than pure TiO2 (4.5%), pure WO3 (4.1%), TiO2@WO3 (68%), MnO x @TiO2@WO3 (76%), TiO2@WO3@Au (89%).

[0078] Catalyst cycle test

[0079] Weigh 50 mg of MnO prepared in Example 1 x The @TiO2@WO3@Au composite catalyst was added to 50 ml of a 10 mg / L phenol solution, placed in the dark and stirred for 30 minutes to reach equilibrium, and then photocatalytic reaction was carried out under a xenon lamp (300W) light source system. Samples were taken every 10 minutes for a total of 100 minutes of irradiation. After filtration, the concentration of phenol in the supernatant was determined by high performance liquid chromatography (the chromatographic column was C18 (length 250 mm, inner diameter 4 mm)), and the eluent: the ratio of methanol to water was 60%:40%, volume ratio). The filtered catalyst was washed 3 times with water and ethanol respectively, dried at 60°C for 8 hours, and added again to 50 ml of a 10 mg / L phenol solution. The photocatalytic reaction was carried out under the same conditions. The same operation was repeated 4 times. The results of the cyclic experiment are shown in Fig. 9 .from Fig. 9 It can be seen that after 4 cycles, the MnO x The @TiO2@WO3@Au composite catalyst did not significantly reduce the phenol degradation efficiency and could still reach more than 95%.

[0080] Compared with the photocatalysts obtained in Comparative Examples 1 to 3, the MnO x @TiO2@WO3@Au composite photocatalyst has the best performance in degrading phenol. The reason is that MnO x @TiO2@WO3@Au hollow composite microspheres have strong ultraviolet and visible light absorption capabilities and enhanced photogenerated carrier separation capabilities.

[0081] Fig.10 The TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 are given. x @TiO2@WO3, TiO2@WO3@Au, MnO x UV-visible absorption spectrum of @TiO2@WO3@Au hollow composite microspheres; Fig.10 It can be seen that compared with pure TiO2, the hollow composite microsphere photocatalyst MnO xThe light absorption range of @TiO2@WO3@Au can be extended to 540 nm, and the absorption band with a wavelength less than 450 nm is contributed by the excellent visible light capture ability of TiO2@WO3. The absorption peak between 450 nm and 540 nm is the surface plasmon resonance absorption of the introduced Au nanoparticles. Therefore, the prepared hollow composite microsphere photocatalyst MnO x @TiO2@WO3@Au achieves enhanced absorption of ultraviolet and visible light.

[0082] Fig.11 and Fig.12 The TiO2@WO3, MnO prepared in Comparative Examples 1-3 and Example 1 are given respectively. x @TiO2@WO3, TiO2@WO3@Au, MnO x Fluorescence spectrum and surface photovoltage spectrum of @TiO2@WO3@Au hollow composite microspheres. Fig.11 It can be seen that: MnO x The fluorescence intensity of @TiO2@WO3@Au is the lowest, indicating that the efficiency of photogenerated carrier recombination luminescence is very low, which indirectly proves the enhancement of photogenerated carrier separation ability. Fig.12 It can be seen that: MnO x The surface photovoltage signal of @TiO2@WO3@Au is negative and has the strongest intensity. This result shows that MnO x The photogenerated electrons of @TiO2@WO3@Au hollow composite microspheres are transferred to the surface of Au nanoparticles, and the dual co-catalysts and heterojunction can enhance the photogenerated carrier separation ability.

Claims

1. A method for preparing a hollow composite microsphere photocatalyst containing dual promoters, characterized in that: The following steps are involved: 1) Hollow MnO x @TiO2 nanospheres are dispersed in deionized water, and then ethylene glycol is added to disperse them evenly; 2) Add Na2WO4•2H2O to the mixed solution obtained in step 1), and then place in a 60-85°C water bath and stir for 10-50 minutes; 3) Add hydrochloric acid to the mixed solution of step 2), stir and react for 1-4 hours, centrifuge, wash and dry, and then heat treat at 500-700℃ for 2-5 hours to obtain MnO x @TiO2@WO3 microspheres; 4) The product MnO obtained in step 3) x The @TiO2@WO3 microspheres are dispersed in deionized water, and then HAuCl4·4H2O aqueous solution is added, and the mixture is irradiated under a 200-400W xenon lamp light source system for 1-4 minutes under stirring, and then centrifuged and the product is collected, washed, and dried to obtain the product.

2. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 1, characterized in that: In step 1), the hollow MnO x The mass ratio of TiO2 nanospheres to deionized water is 1:1000-1200, hollow MnO x @The mass ratio of TiO2 nanospheres to ethylene glycol is 1:30-50.

3. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 1, characterized in that: In step 2), the Na2WO4•2H2O and the hollow MnO x @The molar ratio of TiO2 nanospheres is 0.5-2:

10.

4. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 1, characterized in that: In step 3), the molar concentration of the added hydrochloric acid is 0.4-0.6 mol / L, and the mass ratio of hydrochloric acid to Na2WO4•2H2O is 1000:1-3.

5. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 1, characterized in that: In step 4), the MnO x The mass ratio of @TiO2@WO3 microspheres to deionized water is 1-3:1000, and the mass ratio of HAuCl4·4H2O to MnO x The mass ratio of @TiO2@WO3 microspheres is 1-3:

20.

6. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 1, characterized in that: In step 1), the hollow MnO x @TiO2 nanospheres were prepared by the following steps: SiO2@MnO x The nano-microspheres are dispersed in anhydrous ethanol and mixed with concentrated ammonia water under ultrasonic action, and then tetrabutyl titanate is added, and the reaction is carried out under continuous mechanical stirring in a constant temperature water bath at 40-50°C for 20-30 hours, and the product is separated and collected, washed, and treated with a NaOH solution with a molar concentration of 1-3 mol / L at room temperature for 4-6 hours, centrifuged, washed, and dried to obtain the product.

7. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 6, characterized in that: The SiO2@MnO x The nanospheres are prepared by the following steps: ultrasonically dispersing the SiO2 template in deionized water, then adding KMnO4, the mass ratio of KMnO4 to SiO2 template is 1:3-5, stirring for 20-40 minutes, transferring to a reactor and reacting at 100-200°C for 4-10 hours. After the reaction is completed, cooling to room temperature, separating and collecting the product, washing and drying, the nanospheres are obtained.

8. The method for preparing the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 7, characterized in that: The SiO2 template is prepared by the following steps: dispersing tetraethyl orthosilicate in anhydrous ethanol, adding concentrated ammonia water and deionized water under stirring at room temperature and continuously stirring for 20-30 hours, and after the reaction is completed, centrifuging, washing and drying to obtain the SiO2 template; the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 1:30-60; the mass ratio of tetraethyl orthosilicate to concentrated ammonia water and deionized water is 1:4-6:1-3.

9. A hollow composite microsphere photocatalyst containing dual promoters prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the hollow composite microsphere photocatalyst containing dual promoters as claimed in claim 9 in visible light photocatalytic degradation of phenol.

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