Ag-loaded rare earth metal doped composite photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses an Ag-loaded rare earth metal doped composite photocatalyst as well as a preparation method and application thereof. Sodium tungstate and bismuth nitrate are used as basic raw materials, ytterbium oxide, thulium oxide and silver nitrate are used as doping raw materials, and Bi2WO6: Yb < 3 + >, Tm < 3 + > / Ag is prepared by a hydrothermal method. The Ag-loaded and ytterbium-thulium rare earth co-doped Bi2WO6: Yb < 3 + >, Tm < 3 + > / Ag composite photocatalyst prepared by the invention inhibits the recombination of photon-generated carriers, and can effectively improve the energy conversion efficiency, thereby improving the near-infrared light catalytic efficiency. The Bi2WO6: Yb < 3 + >, Tm < 3 + > / Ag is used for degrading organic pollutants under irradiation of near-infrared light, and the Bi2WO6: Yb < 3 + >, Tm < 3 + > / Ag has important practical application value in environmental purification and clean energy production.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and specifically relates to Ag-loaded rare earth metal-doped Bi2WO6:Yb prepared by a hydrothermal method 3+ ,Tm 3+ / Ag composite photocatalyst and its application. Background Technique

[0002] With the development of modern social technologies, the environmental pollution problem of the earth has become increasingly serious. Therefore, there is an urgent need to develop clean and renewable energy, and thus photocatalytic technology has received extensive attention. Photocatalytic materials have the characteristics of CO2 photoreduction, hydrogen production, photocatalytic nitrogen fixation, and degradation of harmful substances to solve the energy and environmental problems faced by humans. Due to the unique physical and chemical properties of Bi2WO6, it has attracted great attention in recent years. Bi2WO6 has good photocatalytic activity, which is related to the special Aurivillius layered structure composed of WO6 octahedrons and Bi-O-Bi layers. However, unfortunately, most of the visible light is missed, and due to the rapid recombination of photo-generated electron-hole pairs, the photocatalytic activity of pure Bi2WO6 is still low. To meet the challenges of practical applications, it is necessary to inhibit the recombination of electrons and holes. It is known that the photocatalytic activity is affected by various factors, and doping has been proven to be an effective way to semiconductorize Bi2WO6. Due to its excellent structural, electrical, and optical properties, Bi2WO6 retains its potential as a photocatalytic material for environmental and energy conversion. The N-type semiconductor characteristics and the band gap of 2.6-2.8 eV enable the photoactivity of Bi2WO6 to work in the visible light range, but its quantum efficiency is still very low. Its weak visible light absorption response, high charge recombination, small specific surface area, and easy recombination of photo-generated electrons and holes result in its small photocatalytic activity.

[0003] The doping modification method is a common and effective means to improve the electronic structure and surface properties of semiconductor materials, which is mainly divided into non-metal element doping and metal element doping. Bi2WO6 has a layered structure, which is conducive to the uniform doping of dopants. In recent years, it has been proven that Ag-modified semiconductors are promising in enhancing photocatalytic activity and can achieve efficient separation of electron-hole pairs. Summary of the Invention

[0004] In order to solve the above existing technical problems, the purpose of the present invention is to provide a composite photocatalyst loaded with Ag and doped with rare earth metals, its preparation method and application.

[0005] To achieve the above invention purpose, the technical solution adopted by the present invention is: a composite photocatalyst loaded with Ag and doped with rare earth metals, and the composite photocatalyst loaded with Ag and doped with rare earth metals is Bi2WO6:Yb 3+ ,Tm3+ Bi2WO6:Yb / Ag composite photocatalyst; in a molar ratio of Bi2WO6:Yb 3+ :Tm 3+ :Ag = 1:0.15:0.0075:(0.005 - 0.015).

[0006] A preparation method of an Ag-loaded rare earth metal-doped composite photocatalyst, comprising the following steps:

[0007] Dropwise add a bismuth tungstate solution with a pH of 0.7 - 1.3 to a bismuth nitrate solution, and then successively add a solution containing Yb 3+ solution, a solution containing Tm 3+ solution and a solution containing Ag + solution, heat and stir, place it in a reaction kettle, heat it in an oven, centrifuge and wash, dry, sinter at high temperature, and grind to obtain Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst.

[0008] Preferably, in the above preparation method, for the bismuth nitrate solution, a small amount of concentrated nitric acid is added when preparing the bismuth nitrate solution, and at the same time, the heating temperature is controlled at 60 - 90 °C and the heating time is 0.5 - 1 h.

[0009] Preferably, in the above preparation method, the preparation method of the solution containing Yb 3+ solution is: take an appropriate amount of ytterbium oxide in concentrated nitric acid, heat and stir to dissolve, evaporate to dryness and then add an appropriate amount of deionized water to obtain the solution containing Yb 3+ solution.

[0010] Preferably, in the above preparation method, the preparation method of the solution containing Tm 3+ solution is: take an appropriate amount of thulium oxide in concentrated nitric acid, heat and stir to dissolve, evaporate to dryness and then add an appropriate amount of deionized water to obtain the solution containing Tm 3+ solution.

[0011] Preferably, in the above preparation method, the heating and stirring is: heating and stirring at 60 - 90 °C for 2 - 3 h.

[0012] Preferably, in the above preparation method, the heating in the oven is: heating at 140 - 180 °C for 20 - 22 h.

[0013] Preferably, in the above preparation method, the drying is: drying at 60 - 80 °C for 12 - 15 h.

[0014] Preferably, in the above preparation method, the high-temperature sintering is: controlling the heating rate at 4 - 6 °C / min, heating to 500 - 550 °C, and calcining for 4 - 5 h.

[0015] Application of a composite photocatalyst doped with Ag-loaded rare earth metals in the photocatalytic degradation of organic dyes under near-infrared light

[0016] Preferably, the organic dye is Rhodamine B

[0017] The beneficial effects of the present invention are as follows

[0018] 1. In the present invention, ytterbium oxide, thulium oxide and silver nitrate are used to modify Bi2WO6 to prepare a photocatalytic material Bi2WO6:Yb 3+ ,Tm 3+ / Ag. After treatment, Bi2WO6 can achieve infrared photocatalysis under the irradiation of 980 nm infrared light, and at the same time show a lower electron-hole recombination rate, improving the photocatalytic activity of Bi2WO6

[0019] 2. The Ag-loaded and ytterbium-thulium rare earth co-doped Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst prepared in the present invention inhibits the recombination of photo-generated carriers, can effectively improve the energy conversion efficiency, and thus improve the near-infrared photocatalytic efficiency. Using it to degrade organic pollutants under near-infrared light irradiation, Bi2WO6:Yb 3+ ,Tm 3+ / Ag has important practical application value in environmental purification and clean energy production Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings

[0021] Figure 1 XRD patterns of Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalysts with different molar ratios

[0022] Among them, a: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ , b: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 0.5% Ag, c: Bi2WO6: 15% Yb 3+ , 075% Tm 3+ / 1% Ag, d: Bi2WO6: 15% Yb 3+, 0.75% Tm 3+ / 1.5% Ag.

[0023] Figure 2 are the upconversion luminescence images at 980 nm of Bi2WO6:Yb 3+ , Tm 3+ / Ag composite photocatalysts;

[0024] Among them, A: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ , B: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 0.5% Ag, C: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag, D: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1.5% Ag.

[0025] Figure 3 are the curves of the photocatalyst for catalytic degradation of Rhodamine B under near-infrared light;

[0026] Among them, a: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ ; b: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag.

[0027] Figure 4 are the comparative diagrams of the photocatalyst for catalytic degradation efficiency of Rhodamine B under near-infrared light;

[0028] Among them, A: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ ; B: Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag. Specific Embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0030] In the first aspect of the embodiments of the present invention, a composite photocatalyst doped with Ag-loaded rare earth metals is provided. The Ag-loaded rare earth metal-doped composite photocatalyst is Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst; by molar ratio, Bi2WO6:Yb 3+ :Tm 3+ :Ag = 1:0.15:0.0075:(0.005 - 0.015).

[0031] Specifically, Ag forms a Schottky junction on the surface of Bi2WO6:Yb 3+ ,Tm 3+ , introducing the localized surface plasmon resonance (LSPR) effect. Their synergistic effect optimizes the band structure and the separation efficiency of photo-generated carriers of Bi2WO6:Yb 3+ ,Tm 3+ . The dopant hybridizes with the original molecular orbitals of Bi2WO6:Yb 3+ ,Tm 3+ , thereby changing its band structure, electronic structure and optical properties. The Bi2WO6:Yb 3+ ,Tm 3+ / Ag photocatalyst loaded with Ag and co-doped with ytterbium and thulium rare earths has a narrower band gap, lower band gap energy, longer fluorescence lifetime, improves the utilization efficiency of the solar spectrum, and also reduces the recombination rate of photo-generated electrons and holes, thus effectively improving the photocatalytic performance.

[0032] In the second aspect of the embodiments of the present invention, a preparation method of a composite photocatalyst doped with Ag-loaded rare earth metals is provided, including the following steps:

[0033] Dropwise add a bismuth tungstate solution with a pH of 0.7 - 1.3 to a bismuth nitrate solution, and then sequentially add a solution containing Yb 3+ solution, a solution containing Tm 3+ solution and a solution containing Ag + solution. Heat and stir at 60 - 90 °C for 2 - 3 h, put it into a reaction kettle, heat in an oven at 140 - 180 °C for 20 - 22 h, centrifuge and wash, dry at 60 - 80 °C for 12 - 15 h, and finally place it in a muffle furnace, control the heating rate at 4 - 6 °C / min, heat up to 500 - 550 °C, calcine for 4 - 5 h, and grind to obtain Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst.

[0034] Specifically, the present invention prepares Bi2WO6:Yb 3+ ,Tm 3+Ag composite photocatalyst. This method is convenient and simple to operate, and has advantages such as low-temperature synthesis and morphology control. The process conditions have an important impact on hydrothermal synthesis, such as temperature, time, solution pH value, and sealant. During the synthesis of nanomaterials, it is a challenge to synthesize pure component materials using any synthesis method, but the hydrothermal method is a good solution to these problems.

[0035] In the third aspect of the embodiments of the present invention, there is provided an application of an Ag-loaded rare earth metal-doped composite photocatalyst in the catalytic degradation of organic dyes under near-infrared light.

[0036] Specifically, the Bi2WO6:Yb 3+ ,Tm 3+ / Ag photocatalyst loaded with Ag and co-doped with ytterbium and thulium rare earths has a narrower band gap, lower band gap energy, and longer fluorescence lifetime. While improving the utilization efficiency of the solar spectrum, it also reduces the recombination rate of photo-generated electrons and holes, thus effectively improving the photocatalytic performance.

[0037] Example 1 Ag-loaded rare earth metal-doped composite photocatalyst (1) Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ Photocatalyst

[0038] The preparation method includes the following steps:

[0039] 1. Preparation of bismuth nitrate solution: Take 0.97 g (0.02 mol) of bismuth nitrate in 47 mL of deionized water and 3 mL of concentrated nitric acid, and heat and stir to dissolve at 80 °C for 1 h.

[0040] 2. Preparation of bismuth tungstate solution: Take 0.33 g (0.01 mol) of sodium tungstate in 20 mL of deionized water, fully stir and dissolve, and adjust the pH value to 1 with dilute nitric acid.

[0041] 3. Preparation of Yb 3+ solution: Take 0.985 g (0.05 mol) of ytterbium oxide in 20 mL of concentrated nitric acid, heat and stir to dissolve, evaporate to dryness, and then add 100 mL of deionized water to obtain a Yb 3+ solution with a concentration of 0.0005 mol / mL containing Yb 3+ solution.

[0042] 4. Preparation of Tm 3+ solution: Take 0.9646 g (0.05 mol) of thulium oxide in 20 mL of concentrated nitric acid, heat and stir to dissolve, evaporate to dryness, and then add 100 mL of deionized water to obtain a Tm 3+ solution with a concentration of 0.0005 mol / mL containing Tm 3+ solution.

[0043] 5. Dropwise add the bismuth tungstate solution prepared in step 2 into the bismuth nitrate solution prepared in step 1, and then sequentially add 3 mL of the Yb 3+ solution with a concentration of 0.0005 mol / mL containing Yb 3+ solution, 0.15 mL of the Tm 3+ solution with a concentration of 0.0005 mol / mL containing Tm 3+ solution. Heat and stir at 80 °C for 2 h. Put the obtained mixed solution into a reaction kettle, and then place it in an oven at 160 °C for heat reaction for 20 h. Take it out, centrifuge and wash three times with ethanol and deionized water respectively. Take the precipitate and dry it in an oven at 80 °C for 12 h. Then transfer the product to a crucible and sinter it at a high temperature of 550 °C in a muffle furnace for 4 h (heating rate: 5 °C / min). Take it out and grind it to obtain a molar ratio of Bi2WO6:Yb 3+ :Tm 3+ = 1:0.15:0.0075 of Bi2WO6:Yb 3+ ,Tm 3+ photocatalyst, labeled as Bi2WO6:15%Yb 3+ ,0.75%Tm 3+ photocatalyst.

[0044] (II) Bi2WO6:15%Yb 3+ ,0.75%Tm 3+ / 0.5%Ag composite photocatalyst

[0045] The preparation method includes the following steps:

[0046] 1. Preparation of bismuth nitrate solution: The same as (I).

[0047] 2. Preparation of bismuth tungstate solution: The same as (I).

[0048] 3. Preparation of the Yb 3+ solution: The same as (I).

[0049] 4. Preparation of the Tm 3+ solution: The same as (I).

[0050] 5. Preparation of the Ag + solution: Take 0.4246 g (0.025 mol) of silver nitrate in 500 mL of deionized water, stir and dissolve it to obtain an Ag + solution with a concentration of 0.00005 mol / mL containing Ag + solution.

[0051] 6. Dropwise add the bismuth tungstate solution prepared in step 2 into the bismuth nitrate solution prepared in step 1, and then sequentially add 3 mL of Yb 3+A solution containing Yb with a concentration of 0.0005 mol / mL 3+ solution, 0.15 mL of Tm 3+ A solution containing Tm with a concentration of 0.0005 mol / mL 3+ solution and 1 mL of Ag + A solution containing Ag with a concentration of 0.00005 mol / mL + solution, heat and stir at 80 °C for 2 h, put the obtained mixture into a reaction kettle, and then place it in an oven at 160 °C for heat reaction for 20 h; take it out, wash it centrifugally three times with ethanol and deionized water respectively, take the precipitate, dry it in an oven at 80 °C for 12 h, then transfer the obtained product to a crucible, sinter it at a high temperature of 550 °C in a muffle furnace for 4 h (heating rate: 5 °C / min), take it out and grind it to obtain the molar ratio, Bi2WO6:Yb 3+ :Tm 3+ :Ag = 1:0.15:0.0075:0.005 of Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst, labeled as Bi2WO6:15% Yb 3+ ,0.75% Tm 3+ / 0.5% Ag composite photocatalyst.

[0052] (III) Bi2WO6:15% Yb 3+ ,0.75% Tm 3+ / 1% Ag composite photocatalyst

[0053] The preparation method includes the following steps:

[0054] 1. Preparation of bismuth nitrate solution: The same as (I).

[0055] 2. Preparation of bismuth tungstate solution: The same as (I).

[0056] 3. Preparation of the solution containing Yb 3+ solution: The same as (I).

[0057] 4. Preparation of the solution containing Tm 3+ solution: The same as (I).

[0058] 5. Preparation of the solution containing Ag + solution: The same as (II).

[0059] 6. Dropwise add the bismuth tungstate solution prepared in step 2 into the bismuth nitrate solution prepared in step 1, and then successively add 3 mL of Yb 3+ A solution containing Yb with a concentration of 0.0005 mol / mL 3+ solution, 0.15 mL of Tm 3+ A solution containing Tm with a concentration of 0.0005 mol / mL 3+solution and 2 mL of Ag + solution containing Ag with a concentration of 0.00005 mol / mL + The solution was heated and stirred at 80 °C for 2 h. The resulting mixture was placed in a reaction kettle and then heated in an oven at 160 °C for 20 h. After taking it out, it was centrifugally washed three times with ethanol and deionized water respectively. The precipitate was dried in an oven at 80 °C for 12 h, and then the product was transferred to a crucible and sintered at a high temperature of 550 °C for 4 h in a muffle furnace (heating rate: 5 °C / min). After taking it out and grinding, the molar ratio of Bi2WO6:Yb 3+ :Tm 3+ :Ag = 1:0.15:0.0075:0.01 Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst, labeled as Bi2WO6:15% Yb 3+ ,0.75% Tm 3+ / 1% Ag composite photocatalyst.

[0060] (IV) Bi2WO6:15% Yb 3+ ,0.75% Tm 3+ / 1.5% Ag composite photocatalyst

[0061] The preparation method includes the following steps:

[0062] 1. Preparation of bismuth nitrate solution: same as (I).

[0063] 2. Preparation of bismuth tungstate solution: same as (I).

[0064] 3. Preparation of solution containing Yb 3+ solution: same as (I).

[0065] 4. Preparation of solution containing Tm 3+ solution: same as (I).

[0066] 5. Preparation of solution containing Ag + solution: same as (II).

[0067] 6. The bismuth tungstate solution prepared in step 2 was added dropwise to the bismuth nitrate solution prepared in step 1, and then 3 mL of Yb 3+ solution containing Yb with a concentration of 0.0005 mol / mL, 0.15 mL of Tm 3+ solution containing Tm with a concentration of 0.0005 mol / mL, and 3 mL of Ag 3+ solution containing Ag with a concentration of 0.00005 mol / mL 3+ were added in sequence. + solution containing Ag with a concentration of 0.00005 mol / mL +The solution was heated and stirred at 80 °C for 2 h. The obtained mixture was put into a reaction kettle and then placed in an oven at 160 °C for heat reaction for 20 h. After taking out, it was centrifugally washed three times with ethanol and deionized water respectively. Then the precipitate was dried in an oven at 80 °C for 12 h. Then the obtained product was transferred to a crucible and sintered at a high temperature of 550 °C in a muffle furnace for 4 h (heating rate: 5 °C / min). After taking out and grinding, the molar ratio of Bi2WO6:Yb 3+ :Tm 3+ :Ag = 1:0.15:0.0075:0.015 of Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst, labeled as Bi2WO6:15%Yb 3+ ,0.75%Tm 3+ / 1.5%Ag composite photocatalyst.

[0068] (V) Performance testing

[0069] Figure 1 The XRD patterns of Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalysts with different molar ratios prepared. Among them, (a) is Bi2WO6:15%Yb 3+ ,0.75%Tm 3+ without Ag modification, (b) is Bi2WO6:15%Yb 3+ ,0.75%Tm 3+ / 0.5%Ag, (c) is Bi2WO6:15%Yb 3+ ,075%Tm 3+ / 1%Ag, (d) is Bi2WO6:15%Yb 3+ ,0.75%Tm 3+ / 1.5%Ag. It can be seen that the X-ray diffraction peaks of the samples can all point well to the orthorhombic phase of Bi2WO6 (JCPDS No. 04-008-0332). The results show that the preparation of Bi2WO6 is successful. The doping of Yb Figure 1 and Tm 3+ and the loading of Ag have little effect on the crystal phase of the Bi2WO6 substrate. And no characteristic diffraction peaks of ytterbium, thulium single substances, Ag and oxides are found in the XRD pattern, indicating that Bi2WO6:Yb 3+ loaded with Ag and co-doped with ytterbium and thulium ions has been successfully prepared. 3+ ,Tm 3+ / Ag.

[0070] Figure 2 The XRD patterns of Bi2WO6:Yb 3+ ,Tm3+ Upconversion luminescence image at 980 nm of Bi2WO6 / Ag composite photocatalyst. Among them, (A) is Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ without Ag modification, (B) is Bi2WO6: 15% Yb 3+ , 0.75% Tm 3 + / 0.5% Ag, (C) is Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag, (D) is Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1.5% Ag. It can be seen that with the loading of Ag, the upconversion luminescence at 980 nm of Bi2WO6: Yb Figure 2 , Tm 3+ , Tm 3+ is enhanced, and the luminescence of Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag is the strongest.

[0071] Example 2

[0072] Using Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ photocatalyst and Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag composite photocatalyst to conduct performance tests on photocatalytic materials.

[0073] The method is as follows: Weigh 0.1 g of the photocatalyst and place it in a condensation cup, and add 30 mL of rhodamine B (RhB) solution with a concentration of 10 mg / L to be degraded. Considering that the sample has a certain adsorption property, first stir the rhodamine B solution mixed with the photocatalyst in the dark for 30 min, and take 2.5 mL of samples before and after the dark treatment to form an adsorption-desorption equilibrium state between the photocatalyst and rhodamine B, avoiding errors caused by adsorption. Then, using a 980 nm laser as the light source, align the light source with the photocatalytic system to be tested. The whole process is strictly protected from sunlight. Take 2.5 mL of samples every 2 h, and the photocatalytic process lasts for 8 h. Place the sampled liquid in a centrifuge and centrifuge it at 8000 rpm for 5 min. Then take 2 mL of the supernatant in the tube and place it in a cuvette, and use a UV-3600 to measure the residual rhodamine B concentration in the sample liquid, and evaluate the catalytic performance of the catalyst sample based on the absorbance of the sample liquid.

[0074] Figure 3 For (a) Bi2WO6: 15% Yb 3+ , 0.75% Tm3+ , (b) Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag composite photocatalyst for catalytic degradation of Rhodamine B under near-infrared light. As Figure 3 can be seen, under the irradiation of 980 nm light, the absorption intensity of the characteristic absorption peak of the RhB solution at 550 nm gradually decreases over time, indicating that the molecular structure of RhB is destroyed, resulting in a decrease in its absorbance. Thus, Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ and Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag catalysts all have infrared photocatalytic performance to a certain extent.

[0075] Figure 4 is the comparison chart of the catalytic degradation efficiency of Rhodamine B by photocatalysts under near-infrared light. Among them, A is Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ , B is Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag. As Figure 4 can be seen, the Ag-loaded and ytterbium-thulium rare-earth co-doped Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag photocatalysis has a higher degradation efficiency than Bi2WO6: 15% Yb without Ag loading 3+ , 0.75% Tm 3+ . After the same near-infrared light irradiation time, the degradation efficiency of Rhodamine B by Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ is 14.8%, and the degradation efficiency of Rhodamine B by Bi2WO6: 15% Yb 3+ , 0.75% Tm 3+ / 1% Ag is 21.6%. Thus, it can be seen that the near-infrared photocatalytic performance of Bi2WO6: Yb 3+ , Tm 3+ is enhanced after loading Ag.

[0076] Those skilled in the art can easily understand that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed. The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application. The above is only the preferred implementation manner of this application. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of this application, several improvements and variations can still be made, and these improvements and variations should also be regarded as within the protection scope of this application.

Claims

1. A composite photocatalyst doped with Ag-loaded rare earth metals, characterized in that, The Ag-loaded rare earth metal-doped composite photocatalyst is Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst; in terms of molar ratio, Bi2WO6:Yb 3+ :Tm 3+ :Ag = 1:0.15:0.0075:(0.005 - 0.015).

2. The preparation method of a composite photocatalyst doped with Ag-loaded rare earth metals according to claim 1, characterized in that, The preparation method comprises the following steps: adding a bismuth tungstate solution with a pH of 0.7 - 1.3 dropwise into a bismuth nitrate solution, and then successively adding a solution containing Yb 3+ solution, a solution containing Tm 3+ solution, and a solution containing Ag + solution, heating and stirring, placing it in a reaction kettle, heating in an oven, centrifuging and washing, drying, sintering at a high temperature, and grinding to obtain a Bi2WO6:Yb 3+ ,Tm 3+ / Ag composite photocatalyst.

3. The preparation method according to claim 2, characterized in that, For the bismuth nitrate solution, a small amount of concentrated nitric acid is added during preparation, and at the same time, the heating temperature is controlled at 60-90 °C and the heating time is 0.5-1 h.

4. The preparation method according to claim 2, characterized in that, The Yb-containing 3+ solution preparation method is as follows: Take an appropriate amount of ytterbium oxide, dissolve it in concentrated nitric acid under heating and stirring, add an appropriate amount of deionized water after evaporation to dryness to obtain the Yb-containing 3+ solution.

5. The preparation method according to claim 2, characterized in that, The Tm-containing 3+ solution is prepared as follows: Take an appropriate amount of thulium oxide, dissolve it in concentrated nitric acid by heating and stirring, add an appropriate amount of deionized water after evaporation to dryness to obtain a Tm-containing 3+ solution.

6. The preparation method according to claim 2, wherein The heating and stirring are as follows: heating and stirring at 60-90 °C for 2-3 h; the heating in the oven is as follows: heating at 140-180 °C for 20-22 h.

7. The preparation method according to claim 2, characterized in that, The drying is as follows: drying at 60-80 °C for 12-15 h.

8. The preparation method according to claim 2, wherein The high-temperature sintering is as follows: controlling the heating rate at 4-6 °C / min, heating to 500-550 °C, and roasting for 4-5 h.

9. Application of the composite photocatalyst doped with Ag-loaded rare earth metal in the catalytic degradation of organic dyes under near-infrared light as described in claim 1.

10. The application according to claim 9, characterized in that, The organic dye is Rhodamine B.

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