CN105289673A - A kind of Bi2WO6/Ag3PO4 heterojunction composite photocatalyst and its preparation method and application - Google Patents

Abstract

The invention belongs to the field of photocatalysis and specifically relates to a Bi2WO6/Ag3PO4 heterojunction composite photocatalyst and its preparation method and application. The Bi2WO6/Ag3PO4 heterojunction composite photocatalyst is composed of Bi2WO6 and Ag3PO4, wherein Ag3PO4 nanoparticles are deposited on the Bi2WO6 surface of a three-dimensional layered rod-like structure; and the molar ratio of Bi2WO6 to Ag3PO4 is 1:0.1-10. The preparation method of the invention has a simple process, is easy to control and is low-cost. A Bi2WO6/Ag3PO4 heterojunction structure with visible light response is constructed, photon-generated carrier separation is accelerated, and recombination probability of photogenerated electron-hole pairs is minimized. The Bi2WO6/Ag3PO4 heterojunction composite photocatalyst has high-efficiency photocatalytic activity and stability in visible light, has highly-efficient killing and degradation effects on harmful microbes and dye pollutants in a water body and has good practical value and potential application prospect in fields of water body purification, marine pollution prevention and the like.

Description

A kind of Bi2WO6/Ag3PO4 heterojunction composite photocatalyst and its preparation method and application

technical field

The invention belongs to the field of photocatalysis, and in particular relates to a Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst and a preparation method and application thereof.

Background technique

Photocatalytic technology is a technology that uses light energy for material conversion. Since Japanese scientists Fujishima and Honda first reported in 1972 that _TiO2 can photolyze water to produce hydrogen and oxygen under ultraviolet light, semiconductor photocatalytic technology has received more and more attention. More attention ^[1] . For semiconductor materials, they can generate electron-hole pairs under light conditions, some of the electrons and holes meet and recombine in the bulk phase or on the surface, and the other part of the electrons migrate to the semiconductor surface, which has a strong reduction ability and can be combined with The adsorbed oxygen combines to generate strong oxidizing free radicals; and the holes that migrate to the semiconductor surface have strong oxidizing ability, which can oxidize the OH ^- and H ₂ O adsorbed on the semiconductor surface to generate strong oxidizing free radicals. The radicals, such as ·OH, ·HO ₂ , H ₂ O ₂ and ·O ₂ ^- , etc. ^[2] , can directly interact with the reactants and oxidize and decompose them without secondary pollution. In recent years, the application research of photocatalytic technology has developed very rapidly, because of its outstanding advantages such as high efficiency, non-selectivity, high stability, green and non-toxic, no secondary pollution, low energy consumption, easy operation and low cost, etc., and can Making full use of clean and pollution-free solar energy has been widely used in sewage treatment, waste gas treatment, air purification, sterilization, hydrogen production, _CO2 reduction, etc., and the effect is good.

In recent years, people have done a lot of research on the development of new visible light catalysts, including In ³⁺ , Ce ³⁺ , Bi ³⁺ , Ag ⁺ etc. with d0 and d10 electron configurations. Among them, Bi ₂ WO ₆ is the simplest Aurivillius-type oxide and an n-type direct semiconductor material. Since 1999, Kudo et al. first reported that Bi ₂ WO ₆ has photocatalytic activity under visible light radiation with a wavelength greater than 420nm. After ^[3] , Bi ₂ WO ₆ has attracted more and more attention as a new type of visible photocatalytic material due to its narrow band gap (about 2.7eV), which can be excited by visible light and has high catalytic activity under visible light. More attention ^[4] . However, due to the long migration distance of electron and hole pairs excited in monomeric Bi ₂ WO ₆ , the probability of bulk phase recombination increases, which is not conducive to the rapid separation of electrons and holes, resulting in relatively low photocatalytic activity. Therefore, the construction of composite materials through semiconductor recombination can accelerate electron-hole separation and improve the photocatalytic performance of monomer materials ^[5,6] . Ag ₃ PO ₄ is a new type of high-efficiency photocatalytic material. Its unique indirect band gap, strong oxidation of photo-excited holes in the valence band, and its electron transfer rate is higher than the hole transfer rate, thus promoting the electron- Hole separation makes it have good photocatalytic performance; at the same time, Ag vacancy defects can participate in photoelectron capture, provide more photoexcited holes, and are also conducive to electron-hole separation ^[7] . Therefore, there is a need to construct a composite catalyst.

[1] K. Nakata, A. Fujishima. TiO ₂ photocatalysis: Design and applications [J]. Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2012, 13: 169-189.

[2] X.B.Chen, S.S.Mao. Titaniumdioxide nanomaterials: Synthesis, properties, modifications, and applications [J]. Chemical Reviews, 2007, 107: 2891-2959.

[3] A. Kudo, S. Hijii. H-2orO-2evolutionfromaqueoussolutionsonlayeredoxidephotocatalystsconsistingofBi ³⁺ with6s(2)configurationandd(0)transitionmetalions[J].ChemistryLetters,1999,10:1103-1104.

[4] X.F.Cao, L.Zhang, X.T.Chen, Z.L.Xue. Microwave-assisted solution-phase preparation of flower-like Bi2WO6 and its visible-light-driven photocatalytic properties [J].

[5] Y.Hu, DZLi, Y.Zheng, W.Chen, YHHe, Y.Shao, XZFu, GCXiao. BiVO ₄ /TiO ₂ nanocrystalline heterostructure: Awidespectrum responsive photocatalyst towards the highly efficient decomposition of gaseous benzene [J]. .

[6] ZJ Zhang, WZ Wang, L. Wang, SMSun. Enhancement of visible-light photocatalysis by coupling with narrow-band-gapsemiconductor: Acase study on Bi ₂ S ₃ /Bi ₂ WO ₆ [J]. ACS Applied Materials & Interfaces, 2012, 4:593-597.

[7] Z.G.Yi, J.H.Ye, N.Kikugawa, T.Kako, S.X.Ouyang, H.Stuart-Williams, H.Yang, J.Y.Cao, W.J.Luo, Z.S.Li, Y.Liu, R.L.Withers.Anorthophosphatesemiconductorwithphotooxidationpropertiesundervisible-lightirradiation[ J]. Nature Materials, 2010, 9:559-564.

Contents of the invention

The object of the present invention is to provide a Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst and its preparation method and application in view of the problems existing in the prior art.

To achieve the above object, the present invention adopts the following technical solutions to implement:

A Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst consisting of Bi ₂ WO ₆ and Ag ₃ PO ₄ ; in which Ag ₃ PO ₄ nanoparticles are deposited on the Bi ₂ WO ₆ with three-dimensional layered rod-like structure Surface; the molar ratio of Bi ₂ WO ₆ to Ag ₃ PO ₄ is 1:0.1～10.

The molar ratio of Bi ₂ WO ₆ to Ag ₃ PO ₄ is 1:0.1-5.

A preparation method of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst:

(1) Preparation of Bi ₂ WO ₆ : Disperse Bi(NO ₃ ) ₃ ·5H ₂ O in ultrapure water to obtain a dispersion; at the same time, add Na ₂ WO ₄ ·2H ₂ O into ultrapure water, magnetic Stir until completely dissolved to obtain a solution; then add the above Na ₂ WO ₄ solution dropwise to the above Bi(NO ₃ ) ₃ dispersion under magnetic stirring to obtain a suspension, and adjust the pH of the suspension to 5-9 After stirring, transfer the suspension to a high-pressure reactor, put it into an electric constant temperature blast drying oven at 120-180°C for heat treatment for 12-36 hours, then cool the reactor to room temperature, filter, wash and dry at 40-80°C for 2 Bi ₂ WO ₆ with a three-dimensional layered rod-like structure can be obtained in ~10 hours; wherein, the ratio of Bi(NO ₃ ) ₃ ·5H ₂ O to Na ₂ WO ₄ ·2H ₂ O is 2:1;

(2) Preparation of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst: Disperse the Bi ₂ WO ₆ obtained in step (1) in ultrapure water to obtain a dispersion, and then add AgNO _3. Stir until the mixture is completely dissolved, then add the phosphate-containing precursor solution dropwise, then continue to stir in the dark for 2-8 hours, and then filter, wash and vacuum dry at 40-80°C for 2-10 hours to obtain Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst; wherein, the ratio of the amount of phosphate in the phosphate-containing precursor to the amount of silver ions in AgNO ₃ is 1:3.

In the step (1), the pH value of the suspension is adjusted using NH ₃ ·H ₂ O or NaOH with a concentration of 0.1-5.0 mol/L.

The phosphate-containing precursor in the step (2) is one of Na ₂ HPO ₄ , NaH ₂ PO ₄ , Na ₃ PO ₄ , K ₂ HPO ₄ , KH ₂ PO ₄ or K ₃ PO ₄ .

The ratio of the amount of Bi ₂ WO ₆ to the added AgNO ₃ in the step (2) is 1:0.3-15.

The dispersion in the step (1) and step (2) adopts ultrasonic dispersion for 10-60 minutes, and then magnetic stirring for 10-60 minutes.

An application of a Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst, the application of the Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst as a fungicide in water.

An application of a Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst, the application of the Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst in degrading dyes.

An application of a Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst, the application of the Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst in water body purification.

Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst is applied in water body to catalyze the killing and degradation of harmful microorganisms Pseudomonas aeruginosa (P.aeruginosa) and dye pollutant methylene blue (MB). A 500W xenon lamp is used as the light source, and its wavelength range is 420-760nm; the concentration of the microorganism is 10 ⁶ cfu/mL; the concentration of the methylene blue is 20 mg/L; the Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst The dosage is 1.0mg/mL.

The specific test method for its photocatalytic activity is: use a 500W xenon lamp as the light source, supplemented by a filter; add microorganisms and methylene blue solution into the reactor, and then add Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst, Lighting was started after the dark state adsorption reached equilibrium, and samples were taken at intervals during the lighting process. The concentration of surviving bacteria and the concentration of residual methylene blue were measured by plate counting and ultraviolet-visible spectrophotometry, and the killing rate and degradation rate were calculated. The light source is a xenon lamp with a wavelength range of 420-760nm; the microorganism concentration is 10 ⁶ cfu/mL; the methylene blue concentration is 20mg/L; the Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction compound The amount of photocatalyst used was 1.0 mg/mL.

The beneficial effects of the present invention are:

The present invention constructs a composite material with a heterojunction structure by compounding Ag ₃ PO ₄ and Bi ₂ WO ₆ to accelerate the separation of photogenerated carriers on the surface of the composite material, thereby improving the photocatalytic performance of the composite material. Bi ₂ WO ₆ and Ag ₃ PO ₄ are of great significance in the practical application of the two materials in the field of photocatalysis; specifically:

(1) The preparation method adopted in the present invention has simple process, easy control and low cost;

(2) The Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst constructed by the three-dimensional layered rod-like structure Bi ₂ WO ₆ loaded with Ag ₃ PO ₄ nanoparticles prepared by the present invention has a large specific surface area and good Visible light absorption properties;

(3) Compared with Bi ₂ WO ₆ and Ag ₃ PO ₄ , the Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst prepared by the present invention has significantly improved visible light catalytic activity. ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst can kill 99.99% of microorganisms with a concentration of 10 ⁶ cfu/mL in 20 minutes, and completely degrade methylene blue with a concentration of 20 mg/L within 25 minutes;

(4) The Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst prepared by the present invention has good stability and reusability, and still has high-efficiency photocatalytic activity after 6 repeated uses;

(5) The Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst prepared by the present invention has a heterojunction structure, which accelerates the separation of photogenerated carriers and reduces the recombination probability of photogenerated electron-hole pairs, The visible light catalytic activity and stability are improved, and it has good practical value and potential application prospects in the fields of water body purification and marine antifouling.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) collection of illustrative plates of the prepared sample of the present invention (wherein abscissa is 2θ (angle), unit is degree (degree); Ordinate coordinate is Intensity (strength), unit is a.u. (absolute unit)) ;

Fig. 2 is a scanning electron microscope (FESEM) photo of samples prepared in the present invention: (A) Ag ₃ PO ₄ , (B) Bi ₂ WO ₆ , (C, D) Bi ₂ WO ₆ /Ag ₃ PO ₄ -1;

Fig. 3 is the ultraviolet-visible diffuse reflectance spectrum (UV-DRS) figure (wherein abscissa is Wavelength (wavelength), unit is nm (nanometer), ordinate is Absorbance (absorbance), unit is a.u. (absolute) of the sample prepared by the present invention unit));

Fig. 4 is the survival curve (B) of Pseudomonas aeruginosa in the methylene blue concentration change curve (A) and the photocatalytic bactericidal reaction in the prepared sample photocatalytic degradation reaction of the present invention (wherein the abscissa is Time among the figure A (time) ), the unit is min (minutes), the ordinate is C _t /C ₀ , C ₀ is the initial concentration of methylene blue before the reaction starts, and C _t is the methylene blue concentration when the reaction time is t; the abscissa in B is Time (time) , the unit is min (minute), the ordinate is Celldensity (cell concentration), and the unit is logCcfu/mL (number of colonies));

Figure 5 shows the bactericidal rate (A) and XRD pattern (B) of the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst prepared in Example 2 of the present invention after 6 repeated bactericidal experiments (A Among the figure, the abscissa is Cyclenumbers (repeated use times), the ordinate is Antibacterialrate (sterilization rate), and the unit is %; the abscissa in B is 2θ (angle), and the unit is degree (degree), and the ordinate is Intensity (strength) , the unit is au (absolute unit)).

detailed description

The present invention will be further described through specific examples below, which will help those of ordinary skill in the art to understand the present invention more comprehensively, but the present invention is not limited in any way.

The present invention prepares Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst by hydrothermal synthesis method and in-situ precipitation method. The composite photocatalyst has good visible light absorption performance, and the constructed heterojunction structure accelerates photogeneration The separation of carriers reduces the recombination probability of photogenerated electron-hole pairs, has high photocatalytic activity and stability under visible light, and has efficient killing and degradation effects on harmful microorganisms and dye pollutants in water bodies. It has good practical value and potential application prospect in the fields of water body purification and marine antifouling. At the same time, the preparation method of the composite photocatalyst has the characteristics of simplicity, low cost, good repeatability and the like.

Example 1:

Preparation method of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst:

(1) Preparation of Bi ₂ WO ₆ with a three-dimensional layered rod-like structure by hydrothermal synthesis: Weigh 5.0 mmol Bi(NO ₃ ) ₃ ·5H ₂ O into 30 mL of ultrapure water, ultrasonically disperse for 30 min, and then magnetically stir for 30 min. To obtain a dispersion; at the same time, add 5.0mmolNa ₂ WO ₄ 2H ₂ O to 30.0mL ultrapure water, stir magnetically until completely dissolved to obtain a solution; then add the above Bi(NO ₃ ) ₃ dispersion dropwise to the above Na ₂ WO ₄ solution to obtain a suspension, then use 2.0mol/LNH ₃ ·H ₂ O solution to adjust the pH of the suspension to 7, and then continue to stir for 60 minutes; after the stirring is completed, transfer the suspension to a In a high-pressure reaction kettle lined with ethylene, heat treatment at 160°C for 24 hours in an electric constant temperature blast drying oven; After washing with water and ethanol, and then drying at 60°C for 6 hours, Bi ₂ WO ₆ with a three-dimensional layered rod-like structure can be obtained (see Figures 1-3).

(2) Preparation of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst by in-situ precipitation method: control the molar ratio of Bi ₂ WO ₆ to Ag ₃ PO ₄ to 1:1, and weigh 1.0 mmol Bi ₂ obtained above Add WO ₆ into 30mL ultrapure water, ultrasonically disperse for 30min, and then magnetically stir for 30min to obtain a dispersion; then weigh 3.0mmol AgNO ₃ and add it to the above Bi ₂ WO ₆ dispersion, stir until completely dissolved to obtain a mixed solution; at the same time Add 1.0mmol Na ₂ HPO ₄ ·12H ₂ O into 30mL of ultrapure water, and stir it magnetically to completely dissolve to obtain a solution; then add the above Na ₂ HPO ₄ solution dropwise to the above Bi ₂ WO ₆ and AgNO ₃ In the mixed solution, continue to stir at room temperature in the dark for 5 hours; after the stirring is completed, the product is filtered by suction, and the precipitate obtained by suction filtration is washed with ultrapure water and absolute ethanol in turn, and then dried in a vacuum oven at 60°C for 6 hours. A Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst was obtained, denoted as Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 (see Figures 1-3).

Comparative Example 1:

The preparation method of monomer Ag ₃ PO ₄ :

Prepared by co-precipitation method. Dissolve 3.0mmol AgNO ₃ in 30mL ultrapure water, and stir it magnetically to dissolve completely; at the same time, add 1.0mmol Na ₂ HPO ₄ ·12H ₂ O into 30mL ultrapure water, stir magnetically to dissolve it completely, and obtain the solution respectively; Then, the above-mentioned Na ₂ HPO ₄ solution was added dropwise to the above-mentioned AgNO ₃ solution under magnetic stirring to obtain a suspension, and continued to stir at room temperature in the dark for 5 hours; after the stirring was completed, the product was subjected to suction filtration. The precipitate was washed several times with ultrapure water and absolute ethanol in sequence, and then dried in a vacuum oven at 60°C for 6 hours to obtain a single material of Ag ₃ PO ₄ , denoted as Ag ₃ PO ₄ (see Figure 1-3).

It can be seen from Figure 1 that the curve a is the XRD pattern of the monomer Bi ₂ WO ₆ prepared in Example 1, and the positions of all diffraction peaks are completely consistent with the standard card JCPDS No.73-1126, and they all belong to orthorhombic Bi ₂ WO ₆ , and no impurity phase appeared, it can be confirmed that the sample prepared in Example 1 is pure orthorhombic Bi ₂ WO ₆ . Curve b is the XRD spectrum of the monomer _Ag3PO4 prepared in Comparative Example ₁ , as can be seen from the figure, all the diffraction peaks in the figure correspond to the standard cubic system _Ag3PO4 ( _{JCPDSNo.06-0505} ), And no heterophase diffraction peak appeared, indicating that the sample prepared in Comparative Example 1 was pure cubic Ag ₃ PO ₄ . Curve c in the figure is the XRD pattern of Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst prepared in Example 1, which contains cubic phase Ag ₃ PO ₄ and orthorhombic phase Bi ₂ WO ₆ All the characteristic peaks, indicating that Ag ₃ PO ₄ and Bi ₂ WO ₆ are successfully combined to form a composite material. There are no other impurity peaks in the XRD spectrum of the composite material, indicating that the composite material is only composed of Bi ₂ WO ₆ and Ag ₃ PO ₄ , and no other impurity phases exist.

It can be seen from Fig. 2(A) that the Ag ₃ PO ₄ prepared in Comparative Example 1 is spherical particles with high crystallinity, the size is about 200nm, the particle dispersion is good, and there is no obvious agglomeration phenomenon between crystal grains. It can be seen from Fig. 2(B) that the Bi ₂ WO ₆ prepared in Example 1 is a three-dimensional layered rod-like structure with a length of about 10 μm and a width of about 1 μm. This layered rod-like structure is composed of many regular two-dimensional nanosheets intersecting Stacked, the size of each nanosheet is about 100nm, and the thickness is about 20nm. It can be seen from Figure 2(C) and Figure 2(D) that the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst prepared in Example 1 consists of a three-dimensional layered rod-like structure Bi ₂ WO with a size of about 10 μm ₆ Ag ₃ PO ₄ nanoparticles with a loading particle size of about 50nm are assembled. This layered three-dimensional structure loaded with small particles will have a large specific surface area and good visible light absorption performance.

It can be seen from Figure 3 that Bi ₂ WO ₆ , Ag ₃ PO ₄ and Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 composite materials have good absorption in both ultraviolet and visible light regions, showing good visible light absorption performance. In addition, the combination of Ag ₃ PO ₄ with good visible light absorption performance and Bi ₂ WO ₆ greatly improves the visible light absorption performance of Bi ₂ WO ₆ .

Example 2:

Preparation method of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst:

Prepared by in-situ precipitation method, the difference from Example 1 is that the molar ratio of Bi ₂ WO ₆ to Ag ₃ PO ₄ is controlled to be 1:0.75, and 1.0 mmol Bi ₂ WO ₆ obtained above is weighed and added to 30 mL ultrapure water , ultrasonically dispersed for 30 minutes, and then magnetically stirred for 30 minutes to obtain a dispersion; then weighed 2.25 mmol AgNO ₃ and added it to the above Bi ₂ WO ₆ dispersion, and stirred until completely dissolved to obtain a mixed solution; at the same time, 0.75 mmol Na ₂ HPO ₄ ·12H ₂ O was added to 30mL of ultrapure water, and magnetically stirred to completely dissolve it to obtain a solution; then, the above-mentioned Na ₂ HPO ₄ solution was added dropwise to the above-mentioned Bi ₂ WO ₆ and AgNO ₃ mixed solution, and continued to cool at room temperature Stir in the dark for 5 hours; after the stirring, the product is filtered by suction, and the precipitate obtained by suction filtration is washed with ultrapure water and absolute ethanol in turn, and then dried in a vacuum oven at 60°C for 6 hours to obtain Bi ₂ WO ₆ /Ag ₃ PO ₄ Heterojunction composite photocatalyst, denoted as Bi ₂ WO ₆ /Ag ₃ PO ₄ -0.75.

Example 3:

Preparation method of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst:

Prepared by in-situ precipitation method, the difference from Example 1 is that the molar ratio of Bi ₂ WO ₆ to Ag ₃ PO ₄ is controlled to be 1:0.5, and 1.0 mmol Bi ₂ WO ₆ obtained above is weighed and added to 30 mL ultrapure water , ultrasonically dispersed for 30 minutes, and then magnetically stirred for 30 minutes to obtain a dispersion; then weighed 1.5 mmol AgNO ₃ and added it to the above Bi ₂ WO ₆ dispersion, and stirred until completely dissolved to obtain a mixed solution; at the same time, 0.5 mmol Na ₂ HPO ₄ ·12H ₂ O was added to 30mL of ultrapure water, and magnetically stirred to completely dissolve it to obtain a solution; then, the above-mentioned Na ₂ HPO ₄ solution was added dropwise to the above-mentioned Bi ₂ WO ₆ and AgNO ₃ mixed solution, and continued to cool at room temperature Stir in the dark for 5 hours; after the stirring, the product is filtered by suction, and the precipitate obtained by suction filtration is washed with ultrapure water and absolute ethanol in turn, and then dried in a vacuum oven at 60°C for 6 hours to obtain Bi ₂ WO ₆ /Ag ₃ PO ₄ Heterojunction composite photocatalyst, denoted as Bi ₂ WO ₆ /Ag ₃ PO ₄ -0.5.

Example 4:

Preparation method of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst:

Prepared by in-situ precipitation method, the difference from Example 1 is that the molar ratio of Bi ₂ WO ₆ to Ag ₃ PO ₄ is controlled to be 1:0.25, and 1.0 mmol Bi ₂ WO ₆ obtained above is weighed and added to 30 mL ultrapure water , ultrasonically dispersed for 30 minutes, and then magnetically stirred for 30 minutes to obtain a dispersion; then weighed 0.75 mmol AgNO ₃ and added it to the above Bi ₂ WO ₆ dispersion, and stirred until completely dissolved to obtain a mixed solution; at the same time, 0.25 mmol Na ₂ HPO ₄ ·12H ₂ O was added to 30mL of ultrapure water, and magnetically stirred to completely dissolve it to obtain a solution; then, the above-mentioned Na ₂ HPO ₄ solution was added dropwise to the above-mentioned Bi ₂ WO ₆ and AgNO ₃ mixed solution, and continued to cool at room temperature Stir in the dark for 5 hours; after the stirring, the product is filtered by suction, and the precipitate obtained by suction filtration is washed with ultrapure water and absolute ethanol in turn, and then dried in a vacuum oven at 60°C for 6 hours to obtain Bi ₂ WO ₆ /Ag ₃ PO ₄ Heterojunction composite photocatalyst, denoted as Bi ₂ WO ₆ /Ag ₃ PO ₄ -0.25.

Application example 1:

The Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst obtained above was applied to the visible light catalytic degradation of the dye pollutant methylene blue MB:

A 500W xenon lamp is used as a light source, supplemented by a filter to filter out ultraviolet light, so that the wavelength range is 420-760nm. Add 50mL of 20mg/L methylene blue solution into a 50mL reactor, add 50mg of the photocatalyst prepared by the present invention, carry out the photocatalytic reaction after the dark state adsorption reaches equilibrium, take samples at regular intervals during the reaction process, and take the supernatant after centrifugation. The absorbance of the methylene blue solution at a wavelength of 664nm was measured on a UV-visible spectrophotometer to obtain the residual concentration of the methylene blue solution, and the degradation rate was calculated based on this. The blank experiment and the dark experiment were used as control experiments (see Figure 4A).

It can be seen from Figure 4(A) that methylene blue was almost not degraded in the blank experiment, and the influence on the experiment was negligible. In addition, the dark state experiments show that the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst has a certain adsorption performance due to its large specific surface area, but its influence on the photocatalytic reaction can be ignored. Under visible light, the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 composite photocatalyst showed good photocatalytic activity, and the photocatalytic performance was significantly better than that of monomer Bi ₂ WO ₆ and Ag ₃ PO ₄ . The degradation rate of methylene blue can reach 100% in a short period of time. Therefore, combining Ag ₃ PO ₄ with good visible light absorption performance and photocatalytic activity with Bi ₂ WO ₆ to form a heterojunction structure can effectively separate photogenerated electrons-holes on the surface of the composite material and improve the visible light absorption performance of the composite material. and specific surface area, enhancing the visible light catalytic performance of the composite.

Application example 2:

The Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst obtained above is applied to the water body to kill the harmful microorganism Pseudomonas aeruginosa with visible light:

A 500W xenon lamp is used as a light source, supplemented by a filter to filter out ultraviolet light, so that the wavelength range is 420-760nm. Visible light catalytic bactericidal performance of Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst was evaluated with Pseudomonas aeruginosa (P.aeruginosa, 8.0×10 ⁸ cfu/mL):

First prepare the bacterial suspension, inoculate the stock solution of Pseudomonas aeruginosa into the sterilized LB liquid medium, and then place it in an air constant temperature shaker at 37°C and 150rpm for overnight culture. The cultured bacterial suspension was centrifuged and suspended in 0.01 mol/LPBS (pH=7.4) buffer to obtain a Pseudomonas aeruginosa suspension with a concentration of 8.0×10 ⁸ cfu/mL.

In the photocatalytic experiment, 49.5 mL of sterilized 0.01mol/LPBS (pH=7.4) buffer solution was added to a 50 mL reactor, and then 500 μL of bacterial suspension was added to make the bacterial concentration in the reaction solution 8.0×10 ⁶ cfu/mL. 50mg of the photocatalyst prepared by the present invention. After the dark state adsorption reached equilibrium, the photocatalytic reaction was carried out. During the reaction process, samples were taken at intervals, and the survival rate and bactericidal rate of bacteria were determined by plate counting. The specific steps are: take 1.0mL of the reaction solution, dilute several gradients sequentially with 0.01mol/LPBS (pH=7.4) buffer according to the serial dilution method, and then take 100μL from the solutions of different dilution times to the prepared LB solid culture Spread the bacterial solution evenly on the LB medium. Invert the LB medium, put it into an electric thermostat incubator and incubate at 37°C for 24 hours, count the number of colonies grown on the medium, and obtain the bacterial concentration by counting the corresponding dilution factor to determine the survival rate and sterilization rate of the bacteria. In the experiment, each group of experiments needs to be measured in parallel three times, and the average value is taken as the final result, and the blank experiment and dark state experiment are used as control experiments (see FIG. 4B ).

It can be seen from Figure 4(B) that the number of Pseudomonas aeruginosa has almost no change in the blank experiment, indicating that the influence of visible light can be ignored; while under dark conditions, the number of Pseudomonas aeruginosa has a certain reduction, which is Because the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst contains Ag element, some Ag ⁺ will be released in the aqueous solution, and Ag ⁺ also has certain bactericidal properties, which can interact with bacteria and cause Bacterial apoptosis. However, Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst showed good photocatalytic activity under visible light, and the photocatalytic bactericidal performance was significantly better than monomer Bi ₂ WO ₆ and Ag ₃ PO ₄ . Only about 2.9log of bacteria can survive under 20 minutes of light, and the bactericidal rate can reach 99.99%. If the reaction time is extended to 30 minutes, the concentration of bacteria in the system can be ignored. Therefore, the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst has excellent photocatalytic sterilization and antifouling performance, which can be attributed to the complex formation of Ag ₃ PO ₄ and Bi ₂ WO ₆ to form a heterojunction structure, The separation of photogenerated electrons and holes is accelerated, and the photocatalytic activity of the composite material is improved. At the same time, the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst has a large specific surface area and good visible light absorption performance, resulting in improved visible light catalytic performance and good visible light catalytic bactericidal performance.

Application example 3:

The Bi ₂ WO ₆ /Ag ₃ PO ₄ heterojunction composite photocatalyst obtained above is repeatedly applied in the water body to kill the harmful microorganism Pseudomonas aeruginosa with visible light:

Recover the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst used in the photocatalytic sterilization in Application Example 2, wash it with ultrapure water and absolute ethanol several times, and dry it according to the application example The steps in 2 are carried out for the next photocatalytic sterilization reaction, which is carried out continuously for 6 times, keeping other conditions unchanged (see Figure 5).

It can be seen from Figure 5(A) that the killing rate of bacteria by the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst did not decrease significantly after 6 consecutive reactions, and remained above 99%, showing that Good reusability. The Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst that has been subjected to 6 consecutive photocatalytic sterilization experiments was recovered, washed with ultrapure water and absolute ethanol for multiple times, dried and then tested by XRD, as shown in As shown in Figure 5(B), it can be seen from the figure that after six consecutive photocatalytic sterilization reactions, the crystal structure of the Bi ₂ WO ₆ /Ag ₃ PO ₄ -1 heterojunction composite photocatalyst has not changed, showing With good stability, it has good practical value and potential application prospects in the fields of water body purification and marine antifouling.

Claims (10)

1. a Bi ₂wO ₆/ Ag ₃pO ₄heterojunction composite photocatalyst, is characterized in that: Bi ₂wO ₆/ Ag ₃pO ₄heterojunction composite photocatalyst is by Bi ₂wO ₆and Ag ₃pO ₄composition; Wherein, Ag ₃pO ₄nanoparticle deposition is at the Bi of three-dimensional layering club shaped structure ₂wO ₆surface; Bi ₂wO ₆with Ag ₃pO ₄mol ratio be 1:0.1 ~ 10.

2. Bi according to claim 1 ₂wO ₆/ Ag ₃pO ₄heterojunction composite photocatalyst, is characterized in that: described Bi ₂wO ₆with Ag ₃pO ₄mol ratio be 1:0.1 ~ 5.

3. a Bi according to claim 1 ₂wO ₆/ Ag ₃pO ₄the preparation method of heterojunction composite photocatalyst, is characterized in that:

(1) Bi ₂wO ₆preparation: by Bi (NO ₃) ₃5H ₂o is scattered in ultra-pure water, obtains dispersion liquid; Simultaneously by Na ₂wO ₄2H ₂o joins in ultra-pure water, and magnetic agitation, to dissolving completely, obtains lysate; Then under magnetic stirring by above-mentioned Na ₂wO ₄lysate dropwise joins above-mentioned Bi (NO ₃) ₃in dispersion liquid, obtain suspension, and after regulating pH of suspension to 5 ~ 9 to stir, suspension is transferred in autoclave, put into electric heating constant-temperature blowing drying box 120 ~ 180 DEG C of heat treatment 12 ~ 36h, then reactor is cooled to room temperature, the Bi of three-dimensional layering club shaped structure can be obtained through suction filtration, washing and 40 ~ 80 DEG C of drying 2 ~ 10h ₂wO ₆; Wherein, Bi (NO ₃) ₃5H ₂o and Na ₂wO ₄2H ₂the ratio of the amount of substance of O is 2:1;

(2) Bi ₂wO ₆/ Ag ₃pO ₄the preparation of heterojunction composite photocatalyst: by the Bi obtained in step (1) ₂wO ₆be scattered in ultra-pure water and obtain dispersion liquid, then add AgNO under magnetic stirring ₃, be stirred to and dissolve to obtain mixed liquor completely, then dropwise add the precursor solution of phosphorous acid group, continue lucifuge afterwards and stir 2 ~ 8h, can Bi be obtained through suction filtration, washing and 40 ~ 80 DEG C of vacuum drying 2 ~ 10h ₂wO ₆/ Ag ₃pO ₄heterojunction composite photocatalyst; Wherein, phosphate radical and AgNO in the precursor of phosphorous acid group ₃the ratio of the amount of substance of middle silver ion is 1:3.

4. Bi according to claim 3 ₂wO ₆/ Ag ₃pO ₄the preparation method of heterojunction composite photocatalyst, is characterized in that: regulate suspension pH value to adopt concentration to be the NH of 0.1 ~ 5.0mol/L in described step (1) ₃h ₂o or NaOH.

5. Bi according to claim 3 ₂wO ₆/ Ag ₃pO ₄the preparation method of heterojunction composite photocatalyst, is characterized in that: in described step (2), the precursor of phosphorous acid group is Na ₂hPO ₄, NaH ₂pO ₄, Na ₃pO ₄, K ₂hPO ₄, KH ₂pO ₄or K ₃pO ₄one wherein.

6. Bi according to claim 3 ₂wO ₆/ Ag ₃pO ₄the preparation method of heterojunction composite photocatalyst, is characterized in that: Bi in described step (2) ₂wO ₆with the AgNO added ₃the ratio of amount of substance be 1:0.3 ~ 15.

7. a kind of Bi according to claim 3 ₂wO ₆/ Ag ₃pO ₄the preparation method of heterojunction composite photocatalyst, is characterized in that: disperse to be adopt ultrasonic disperse 10 ~ 60min, then magnetic agitation 10 ~ 60min in described step (1) and step (2).

8. a Bi according to claim 1 ₂wO ₆/ Ag ₃pO ₄the application of heterojunction composite photocatalyst, is characterized in that: described Bi ₂wO ₆/ Ag ₃pO ₄heterojunction composite photocatalyst is as the bactericide in water body.

9. a Bi according to claim 1 ₂wO ₆/ Ag ₃pO ₄the application of heterojunction composite photocatalyst, is characterized in that: described Bi ₂wO ₆/ Ag ₃pO ₄the application of heterojunction composite photocatalyst in degradation of dye.

10. a Bi according to claim 1 ₂wO ₆/ Ag ₃pO ₄the application of heterojunction composite photocatalyst, is characterized in that: described Bi ₂wO ₆/ Ag ₃pO ₄the application of heterojunction composite photocatalyst in water body purification.