Bismuth-based oxyhalide composite catalyst loaded with metal nanoclusters as well as preparation method and application of bismuth-based oxyhalide composite catalyst

Abstract

The invention provides a bismuth-based oxyhalide composite catalyst loaded with metal clusters as well as a preparation method and application of the bismuth-based oxyhalide composite catalyst, and particularly relates to the technical field of photocatalysis. The composite catalyst is prepared from a Bi7Fe2Ti2O17X thin nano sheet, a Bi7Fe2Ti2O17X thin nano sheet and a The Bi7Fe2Ti2O17X thin nanosheet is loaded on the substrate, the metal nanocluster is loaded on the Bi7Fe2Ti2O17X thin nanosheet, X is at least one of Cl, Br and I, and the metal nanocluster is one or more of Cu, Fe, Co, Ag, Pt, Pd, Bi, Au or Ag. The composite material also has a high specific surface area, abundant reaction active sites and excellent photocatalytic degradation and CO2 reduction performance, and can promote the development of a cluster-based new energy technology.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis processes of photocatalytic materials, photocatalytic degradation of organic pollutants and carbon dioxide (CO 2 ) emission reduction field, and particularly relates to a bismuth-based halide oxide composite catalyst loaded with metal nanoclusters, a preparation method thereof and an application thereof. Background Art

[0002] With the rapid growth of the global population and the expansion of the scale of human production and life, environmental pollution and energy crisis have gradually become the main limiting factors restricting people's survival and development. Solar energy has the advantages of rich reserves, clean and pollution-free, and not restricted by regions, and has become one of the energy systems widely concerned by researchers. At present, the main technologies for utilizing solar energy mainly include three types, namely solar cells, photocatalysis, and photothermal conversion. Among them, photocatalytic technology takes semiconductor materials as the core, converts the solar photons incident on the material surface into highly active electron-hole pairs, separates and migrates to the catalyst surface under light excitation, and generates redox reactions. The application scope of photocatalytic technology is wide, from the degradation of organic pollutants such as organic dyes or antibiotics in the environmental field, the decomposition of harmful gases to the reduction of carbon dioxide (CO 2 ) in the energy field, photocatalytic water splitting, etc., which is an effective strategy for environmental pollution and energy crisis.

[0003] Among many photocatalytic materials, titanium dioxide (TiO 2 ) materials have received the most attention due to their advantages such as low price, non-toxicity, and good catalytic effect. However, the common rutile TiO 2 has a relatively wide band gap of 3.2 eV, only responds to ultraviolet light, and has a low utilization rate of sunlight, which severely limits the generation of photogenerated electron-hole pairs and affects the catalytic efficiency. In contrast, visible light accounts for 45% of the solar energy, and the development of new visible light-responsive photocatalysts has become the current research hotspot and focus. Although a large number of visible light catalysts have been studied, their use is still severely restricted, including low quantum yield and photogenerated carrier recombination rate, etc. Therefore, certain strategies need to be adopted to enhance the photocatalytic activity of the catalyst. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the main purpose of the present invention is to provide a bismuth-based halide oxide composite catalyst loaded with metal nanoclusters, a preparation method thereof and an application thereof, which have advantages such as a large spectral absorption range, high carrier transport and separation efficiency, etc., to solve the main problems existing in current catalysts.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] As one aspect of the present invention, there is provided a bismuth-based halogen oxide composite catalyst loaded with metal nanoclusters, the composite catalyst comprising: Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets; and metal nanoclusters loaded on the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets, where X is at least one of Cl, Br, and I, and the metal nanoclusters are one or more metals among Cu, Fe, Co, Ag, Pt, Pd, Bi, Au, or Ag.

[0007] As another aspect of the present invention, there is provided a method for preparing the above-mentioned bismuth-based halogen oxide composite catalyst loaded with metal nanoclusters, comprising the following steps: using Bi 2 O 3 、Fe 2 O 3 、TiO 2 and BiOX as precursor materials, where X = Cl, Br, and / or I, and preparing Bi 7 Fe 2 Ti 2 O 17 X intrinsic material by the molten salt method or the solid-phase method; subjecting the Bi 7 Fe 2 Ti 2 O 17 X intrinsic material to ultrasonic exfoliation or hydrothermal treatment to obtain Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets; under a visible light source, uniformly depositing metal nanoclusters on the surface of the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets to obtain a composite catalyst; where the metal nanoclusters are one or more metals among Cu, Fe, Co, Ag, Pt, Pd, Bi, Au, or Ag.

[0008] As yet another aspect of the present invention, there is provided an application of the above-mentioned bismuth-based halogen oxide composite catalyst loaded with metal nanoclusters, or the bismuth-based halogen oxide composite catalyst loaded with metal nanoclusters obtained by the above-mentioned preparation method, in photocatalytic degradation of organic pollutants and carbon dioxide reduction reaction, where the organic pollutants include at least one of organic dyes or antibiotics.

[0009] Compared with the prior art, the bismuth-based halide oxide composite catalyst loaded with metal nanoclusters, its preparation method and application of the present invention have the following advantages:

[0010] 1. The present invention uses the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets as the intrinsic catalyst, with the band gap ranging between 2.6 - 2.8 eV, a small forbidden band width, a large visible light response range, and can absorb most of the sunlight. In addition, the valence band is mainly composed of O-2p orbitals, which can avoid the oxidation of photo-generated holes, and the material has good stability. On the surface of the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets, metal nanoclusters are loaded, which have a high specific surface area and rich reactive sites. The strong interfacial coupling between the metal nanoclusters and the intrinsic catalyst is conducive to the local surface plasmon effect, enhancing light absorption, and electrons migrate from the metal nanoclusters to Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets, forming a Schottky interface between the two, strengthening the separation and transport efficiency of photo-generated carriers, and contributing to the improvement of visible light catalytic efficiency.

[0011] 2. The present invention uses the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets as the intrinsic catalyst, and metal nanoclusters are loaded on the surface of the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets by in-situ photodeposition method, which can be stably reduced to form metal nanoclusters under visible light source and normal temperature and pressure conditions, with the advantages of simple process method, convenient operation, reaction at normal temperature and pressure, low equipment investment, and being suitable for large-scale industrial production.

[0012] 3. The composite catalyst provided by the present invention shows good visible light degradation effect on organic dyes such as rhodamine B (RhB) and antibiotics such as tetracycline hydrochloride (TCH), and shows good visible light catalytic effect on the CO 2 reduction reaction. This composite catalyst has broad application prospects in the fields of pollutant treatment, photocatalytic carbon dioxide reduction, etc. Description of the Drawings

[0013] Figure 1Photocatalytic mechanism diagram of the composite catalyst provided by the present invention;

[0014] Figure 2 Flow chart for the preparation of the bismuth-based halide oxide composite catalyst loaded with metal nanoclusters according to an embodiment of the present invention;

[0015] Figure 3 Ag / Bi according to an embodiment of the present invention 7 Fe 2 Ti 2 O 17 XRD pattern of the Ag / Bi

[0016] Figure 4 Ag / Bi according to an embodiment of the present invention 7 Fe 2 Ti 2 O 17 TEM image of the Ag / Bi

[0017] Figure 5 Ag / Bi according to an embodiment of the present invention 7 Fe 2 Ti 2 O 17 High magnification XPS results of Ag in the Ag / Bi

[0018] Figure 6 Ag / Bi according to an embodiment of the present invention 7 Fe 2 Ti 2 O 17 Schematic diagram of the potential energy barrier at the interface of the Ag / Bi

[0019] Figure 7 Ag / Bi according to an embodiment of the present invention 7 Fe 2 Ti 2 O 17 Schematic diagram of the action mechanism of the Ag / Bi composite photocatalyst material, where a is the energy band diagram before contact, b is the energy band diagram after contact, and c is the schematic diagram of carrier movement;

[0020] Figure 8 Ag / Bi according to an embodiment of the present invention 7 Fe 2 Ti 2 O 17 Results of photocatalytic degradation of RhB by the Ag / Bi 7 Fe 2 Ti 2 O 17UV-Vis absorption spectra of Cl samples, (b) Prepared Bi 7 Fe 2 Ti 2 O 17 Cl and Ag / Bi 7 Fe 2 Ti 2 O 17 Variation curve of photocatalytic degradation activity of RhB by Cl photocatalyst with time, (c) First-order kinetic fitting curve, (d) k values of RhB degradation by different samples;

[0021] Figure 9 Ag / Bi of the embodiment of the present invention 7 Fe 2 Ti 2 O 17 Result graph of photocatalytic degradation of tetracycline hydrochloride by Cl composite photocatalyst, where (a) Under visible light irradiation, 10 mg / L TCL solution for Ag / Bi 7 Fe 2 Ti 2 O 17 UV-Vis absorption spectra of Cl samples, (b) Prepared Bi 7 Fe 2 Ti 2 O 17 Cl and Ag / Bi 7 Fe 2 Ti 2 O 17 Variation curve of photocatalytic degradation activity of TCH by Cl photocatalyst with time;

[0022] Figure 10 Ag / Bi of the embodiment of the present invention 7 Fe 2 Ti 2 O 17 CO of Cl composite photocatalyst material 2 Reduction result. Specific embodiments

[0023] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0024] In the process of implementing the inventive concept, it was found that through in-situ photodeposition, on the intrinsic catalyst Bi with visible light response 7 Fe 2 Ti 2 O 17X (X = Cl, Br, and / or I) can be stably reduced on the surface to produce metal nanoclusters. The work function matching between the metal nanoclusters and the intrinsic catalyst can form a Schottky contact, which promotes the migration of photo-generated holes from the semiconductor material to the surface of the metal clusters, thereby enhancing the separation and transport of photo-generated carriers and improving the visible light catalytic efficiency. Accordingly, the present invention provides a bismuth-based halide oxide composite catalyst loaded with metal nanoclusters, a preparation method thereof, and an application thereof. Metal clusters are generated by an in-situ photodeposition technique and coupled with the intrinsic catalyst to synergistically enhance the light absorption ability of the catalyst and the separation and transport efficiency of photo-generated carriers. It has the advantages of being green and pollution-free, having high catalytic activity, and being applicable to industrial applications.

[0025] Specifically, according to some embodiments of the present invention, a preparation method of a bismuth-based halide oxide composite catalyst loaded with metal nanoclusters is provided, including the following steps S1 to S3.

[0026] In step S1, using Bi 2 O 3 , Fe 2 O 3 , TiO 2 and BiOX as precursor materials, where X = Cl, Br, and / or I, and using a molten salt method or a solid-phase method to prepare Bi 7 Fe 2 Ti 2 O 17 X intrinsic material.

[0027] In step S2, ultrasonically exfoliating or hydrothermally treating the Bi 7 Fe 2 Ti 2 O 17 X intrinsic material obtained in step S1 to obtain Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets;

[0028] In step S3, under a visible light source, uniformly depositing metal nanoclusters on the surface of the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets obtained in step S2 to obtain a composite catalyst; wherein the metal nanoclusters are one or more metals selected from Cu, Fe, Co, Ag, Pt, Pd, Bi, Au, or Ag.

[0029] The preparation method provided by the present invention uses Bi 7 Fe 2 Ti 2 O 17X intrinsic material is used as a carrier. Through in-situ photodeposition technology, metal reduction reaction can occur under visible light conditions in a relatively short time, and metal nanoclusters can be formed relatively stably and evenly loaded on the surface of the intrinsic material. It has the advantages of simple process method, convenient operation, mild conditions, low equipment investment, and is suitable for industrial mass production.

[0030] In some embodiments of the present invention, in step S1, Bi 7 Fe 2 Ti 2 O 17 The preparation of the X intrinsic material can preferably be prepared by a molten salt method, which specifically includes steps S11 and S12.

[0031] In step S11, the precursor material is ground and mixed with the base molten salt according to a stoichiometric ratio, wherein the base molten salt is one or more of NaX, KX and CsX, and the mass ratio of the precursor material to the base molten salt is 1: (0-100).

[0032] Furthermore, 2 O 3 , Fe 2 O 3 、TiO 2 and BiOX are mixed in a molar ratio of 3:1:2:1, and are fully ground with the base molten salt. The grinding method can be, for example, ball milling, and the grinding time can be 1 to 6 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc., and there is no special limitation, as long as uniform mixing can be achieved and a powder with relatively uniform particles can be formed.

[0033] Further optionally, taking X as Cl as an example, the base molten salt may be, for example, NaCl, KCl, CsCl, a mixture of NaCl and KCl at a molar ratio of 1:1, or a mixture of NaCl and CsCl at a molar ratio of 1:1, etc. When X is Br or I, a similar corresponding molten salt may be selected.

[0034] Further optionally, the mass ratio of the precursor material to the base molten salt can be, for example, 1:0, 1:1, 1:1.7, 1:2, 1:8, 1:10, 1:20, 1:40, 1:60, 1:80, 1:100, etc.

[0035] In step S12, the ground and mixed mixture is calcined, and then repeatedly washed and dried to obtain Bi 7 Fe 2 Ti 2 O 17 X intrinsic material, wherein the heating rate of the calcination treatment is 0.5-10°C / min, the calcination temperature is 500-900°C, and the calcination time is 5-20 h.

[0036] Further optionally, the heating rate of the calcination treatment can be, for example, 0.5 °C / min, 1 °C / min, 2 °C / min, 4 °C / min, 6 °C / min, 8 °C / min, 10 °C / min, etc., the calcination temperature can be, for example, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, etc., and the calcination duration can be, for example, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, etc. The specific calcination treatment conditions can be selected according to the preparation method of the Bi 7 Fe 2 Ti 2 O 17 X intrinsic material, the type of molten salt, etc.

[0037] Further, the Bi 7 Fe 2 Ti 2 O 17 X intrinsic material provided by the present invention is of the Sillén-Aurivillius phase. Through experiments, it is found that in order to obtain a Bi 7 Fe 2 Ti 2 O 17 X intrinsic material with a high quality and the Sillén-Aurivillius phase, it is more preferable to use a mixed molten salt of NaCl and CsCl with a molar ratio of 1:1 or NaCl and KCl with a molar ratio of 1:1 and calcine at a calcination temperature of 700-800 °C for 12-16 hours.

[0038] Among them, as Figure 1 shown, the Bi 7 Fe 2 Ti 2 O 17 X intrinsic material in the Sillén-Aurivillius phase contains a repeating alternating structure of [Bi - O 2 O 2 + layers separated by halogen X 3 Ti 2 Fe 2 O 13 3- perovskite layers, and has good light stability and visible light response.

[0039] In some embodiments of the present invention, in step S2, the Bi 7 Fe 2 Ti 2 O​​17 The X intrinsic material is a layered structure. Experiments have found that ultrathin nanosheets can be exfoliated by ultrasonic exfoliation or hydrothermal treatment, and more active sites are exposed, which is beneficial to the subsequent stable reduction on it to form metal clusters, thereby exerting high catalytic activity.

[0040] Further optionally, the prepared Bi 7 Fe 2 Ti 2 O 17 The size of the X thin nanosheets is 0.25 - 5 μm, for example, it can be 0.25 μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0041] Further optionally, the conditions for ultrasonic exfoliation include: ultrasonic frequency is 10 - 100 kHz, ultrasonic power is 50 - 1000 W, ultrasonic duration is 1 - 100 h, and ultrasonic temperature is 20 - 60 °C; or, the conditions for hydrothermal treatment include: the hydrothermal solvent is one or more of water, ethanol, ethylene glycol, and glycerol, the hydrothermal temperature is 80 - 200 °C, and the duration is 2 - 20 h.

[0042] Further optionally, the ultrasonic frequency can be, for example, 10 KHz, 20 KHz, 40 KHz, 80 KHz, 100 KHz, etc., the ultrasonic power can be, for example, 50 W, 100 W, 150 W, 200 W, 400 W, 600 W, 800 W, 1000 W, etc., the ultrasonic duration can be, for example, 1 h, 10 h, 20 h, 40 h, 60 h, 80 h, 100 h, etc., and the ultrasonic temperature can be, for example, 20 °C, 30°C, 40 °C, 50°C, 60 °C, etc.

[0043] Further optionally, the hydrothermal temperature can be, for example, 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180°C, 200 °C, etc., and the duration can be, for example, 2 h, 4h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, etc.

[0044] In some embodiments of the present invention, step S3 specifically includes steps S31 to S32.

[0045] In step S31, mix the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets with a metal salt solution to obtain a mixed solution.

[0046] Further optionally, when the metal nanoclusters are one or more metals among Cu, Fe, Co, Ag, Pt, Pd, Bi, Au or Ag, the metal salt is a soluble salt solution of these metals, such as nitrate, chloride, sulfate, etc., preferably nitrate.

[0047] Further optionally, the metal element of the metal salt and Bi 7 Fe 2 Ti 2 O 17 The mass ratio of the ultrathin nanosheets of Bi 7 Fe 2 Ti 2 O 17 X to the metal nanoclusters can be (0.1 - 10):100, for example, it can be 0.1:100, 0.3:100, 0.5:100, 0.7:100, 0.9:100, 1:100, 2:100, 4:100, 5:100, 6:100, 8:100, 10:100, etc. The present invention preferably uses (0.1 - 1):100. Based on the ultrathin Bi

[0048] In step S32, the mixed solution is placed under a visible light source for reaction, and the composite catalyst is obtained after separation and drying.

[0049] Further optionally, the reaction temperature can be 20 - 40 °C, for example, it can be 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, etc., and the reaction time can be 5 - 30 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0050] It is worth mentioning that the present invention uses visible light as the light source, and through the in-situ photodeposition method, the loading of metal nanoclusters can be achieved in a short time, such as 5 - 15 min, showing high photoreduction activity.

[0051] Further optionally, the drying temperature can be 50 - 100 °C, for example, it can be 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, etc., and the drying duration can be 1 - 15 h, for example, it can be 1 h, 5 h, 10 h, 15 h, etc.

[0052] Further optionally, the visible light source can be, for example, a xenon lamp. In order to verify that the composite catalyst of the present invention is suitable for photocatalytic reactions under visible light, the light emitted by the xenon lamp can be filtered to remove ultraviolet light as the illumination condition.

[0053] According to some embodiments of the present invention, there is also provided a bismuth-based halogen oxide composite catalyst loaded with metal nanoclusters prepared by the preparation method described above. The composite catalyst includes:

[0054] Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets; and metal nanoclusters loaded on the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets, where X is at least one of Cl, Br, and I, and the metal nanoclusters are one or more metals among Cu, Fe, Co, Ag, Pt, Pd, Bi, Au, or Ag.

[0055] The bismuth-based halogen oxide composite catalyst provided by the present invention uses Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets as a carrier, on which metal nanoclusters are loaded. The band gap ranges between 2.6 - 2.8 eV, the forbidden band width is small, and the visible light response range is large. It can be used as a visible light-responsive photocatalyst, thus making more use of sunlight and exerting its catalytic activity.

[0056] Among them, for the purpose of facilitating the description of the photocatalytic mechanism of the composite catalyst provided by the present invention, as Figure 1 shown, strong interfacial coupling between the metal nanoclusters and the intrinsic catalyst is beneficial to the local surface plasmon effect, enhancing light absorption, and electrons migrate from the metal nanoclusters to Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets, forming a Schottky interface between the two, promoting the migration of photo-generated holes from Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets to the metal nanoclusters, forming an internal electric field from Bi 7 Fe 2 Ti 2 O 17 X thin nanosheets to the metal nanoclusters direction, strengthening the separation and transport efficiency of photo-generated carriers and contributing to the improvement of visible light catalytic efficiency.

[0057] Further preferably, the metal nanoclusters are metal Ag clusters, which are loaded on Bi 7 Fe 2 Ti 2 O 17When it is an X thin nanosheet, it exhibits high catalytic activity.

[0058] Further optionally, based on the total mass of the composite catalyst, the loading amount of the metal nanoclusters is 0.1-10.0 wt%, for example, it can be 0.1 wt%, 1.0 wt%, 5.0 wt%, 7.5 wt%, 10.0 wt%, etc. Bi 7 Fe 2 Ti 2 O 17 The size of the X thin nanosheet is 0.25-5 μm.

[0059] If the loading amount of the above metal nanoclusters is too low, it is not conducive to exerting the catalytic activity. Especially for noble metal nanoclusters, it is difficult to promote photocatalysis through its surface plasmon effect. If the loading amount of the metal nanoclusters is too high, agglomeration is likely to occur, which will also lead to a decline in its catalytic performance.

[0060] Further optionally, the metal nanoclusters are located on the surface of the Bi 7 Fe 2 Ti 2 O 17 X thin nanosheet, and the metal nanoclusters are stacked along the (020) crystal plane of the nanosheet. The size of the metal nanoclusters is 0.1-20 nm, for example, it can be 1 nm, 5 nm, 10 nm, 20 nm, etc.

[0061] According to some embodiments of the present invention, there is provided an application of a bismuth-based halide oxide composite catalyst loaded with metal nanoclusters obtained by the above-mentioned preparation method in the visible light catalytic degradation of organic pollutants and carbon dioxide reduction reaction, wherein the organic pollutants include at least one of organic dyes or antibiotics. Further optionally, the organic dye can be RhB, etc., and the antibiotic can be TCH, etc.

[0062] The technical solution of the present invention will be further described below through specific examples in conjunction with the drawings. It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemical drugs and raw materials used in the following examples are all obtained commercially or prepared by known preparation methods.

[0063] Example 1

[0064] A preparation method of a bismuth-based halide oxide (Bi 7 Fe 2 Ti 2 O 17 Cl) composite catalyst loaded with metal nanoclusters is as Figure 2 shown and includes the following steps:

[0065] Step 1, prepare Bi 7 Fe 2 Ti 2 O 17 Cl intrinsic material

[0066] Sub-step 1.1, mix Bi 2 O 3 (1.39787 g), Fe 2 O 3 (0.1597 g), TiO 2 (0.1597 g), BiOCl (0.2604 g), and a mixture of NaCl and CsCl (3.402 g, NaCl:CsCl = 1:1). Ball mill for 3 h to form a powder with uniform particles;

[0067] Sub-step 1.2, load the mixture into an alumina crucible, calcine at 750 °C for 12 h, cool naturally, wash the product 4 - 5 times with deionized water and ethanol, and dry the sample at 60 °C for 12 h to obtain a dark yellow powder with a nanosheet configuration, namely Bi 7 Fe 2 Ti 2 O 17 Cl intrinsic material.

[0068] Step 2, prepare Bi 7 Fe 2 Ti 2 O 17 Cl ultrathin nanosheets

[0069] Sub-step 2.1, completely disperse 0.3 g of Bi 7 Fe 2 Ti 2 O 17 Cl intrinsic material in 50 mL of absolute ethanol, and then perform ultrasonic treatment at room temperature for 40 h, with an ultrasonic frequency of 40 KHz and an ultrasonic power of 150 W;

[0070] Sub-step 2.2, centrifuge, wash the collected sample, and dry it in an oven at 60 °C for 6 h to obtain Bi 7 Fe 2 Ti 2 O 17 Cl ultrathin nanosheets.

[0071] Step 3, prepare Ag nanocluster-loaded Bi 7 Fe 2 Ti 2 O 17 Cl composite catalyst

[0072] Sub-step 3.1, Disperse 100 mg of Bi 7 Fe 2 Ti 2 O 17 Cl ultrathin nanosheets into 100 mL of deionized water; Add AgNO 3 with different masses (2.5, 5, 7.5, and 10 mg of silver element respectively) to the reaction aqueous solution;

[0073] Sub-step 3.2, Place the mixed solution under a visible light xenon lamp and react for 30 min to finally obtain the Ag / Bi 7 Fe 2 Ti 2 O 17 Cl composite photocatalyst material.

[0074] Structure characterization and performance testing:

[0075] 1. Perform structure detection on the above Bi 7 Fe 2 Ti 2 O 17 Cl intrinsic material and the composite photocatalyst material. The results are as shown in the XRD pattern of Figure 3 . It can be found that the diffraction peaks of Bi 7 Fe 2 Ti 2 O 17 Cl are relatively sharp, indicating high crystallinity. At the same time, the (006) of Ag is found at the diffraction angle position of 55.16°, indicating that the composite material contains Ag clusters. As shown in the TEM pattern of the composite photocatalyst material in Figure 4 , it can be found that the silver nanoclusters are located on the surface of Bi 7 Fe 2 Ti 2 O 17 X ultrathin nanosheets and are stacked along the (020) crystal plane of the nanosheets. As shown in the high-magnification XPS pattern of the Ag element of the composite material in Figure 5 , the positions of Ag-3d3 / 2 and Ag-3d5 / 2 are 373.6 eV and 376.7 eV respectively, which also confirms that the composite material contains Ag clusters. These results confirm that the Ag / Bi 7 Fe 2 Ti 2 O 17 Cl composite photocatalyst material has been successfully prepared in the experiment.

[0076] In addition, the Bi 7 Fe 2 Ti 2 O 17The surface work function of Cl is used to explain the interfacial interaction between Ag clusters and oxohalides. As Figure 6 shown, the calculated work function (Φ) of Bi 7 Fe 2 Ti 2 O 17 Cl is 7.63 eV. For Ag clusters, the Φ value is 4.26 eV. The difference in work function can drive the charge migration at the Ag / Bi 7 Fe 2 Ti 2 O 17 Cl composite material interface. Obviously, the Φ of Bi 7 Fe 2 Ti 2 O 17 Cl is greater than that of metallic Ag (as shown in Figure a of Figure 7 ). When the two are closely combined, electrons will transfer from Ag to Bi 7 Fe 2 Ti 2 O 17 Cl oxohalide until the Fermi level is balanced, as shown in Figure b of Figure 7 . The energy band edges of Bi 7 Fe 2 Ti 2 O 17 Cl bend downward due to the acquisition of electrons, while the bending direction of Ag clusters is opposite. At the same time, Figure 7 in Figure c of Ag / Bi 7 Fe 2 Ti 2 O 17 Cl, the spontaneous charge redistribution at the interface will form an internal electric field (IEF) from Bi 7 Fe 2 Ti 2 O 17 Cl towards the Ag cluster direction, which is beneficial to electron transfer and ultimately leads to an increase in the reaction rate and kinetics.

[0077] 2. The above composite catalytic material is used for photocatalytic degradation of RhB, and the specific steps are as follows:

[0078] Take the ground Ag / Bi with a 5% Ag loading 7 Fe 2 Ti 2 O 1750 mg of the Cl composite photocatalytic material was added to 100 mL of RhB solution (5 mg / L) and stirred in the dark for 30 minutes. Simulating visible light, the solution was irradiated with a xenon lamp, and ultraviolet light below 420 nm was filtered using a filter. The height of the light source from the upper surface of the solution was 10 cm. Every 2.5 minutes, 4 mL of the solution was taken and centrifuged to separate the solution from the powder. The absorption spectrum of the solution was measured using a UV-visible spectrophotometer, and the results are as Figure 8 shown in Figure a of Figure 8 . To more clearly observe its degradation efficiency, a concentration-time change curve was made, as shown in Figure b of Figure 8 . It can be found that after 10 minutes of illumination, the concentration of RhB becomes 0, indicating that it is almost completely degraded. Subsequently, the first-order kinetic results were calculated (as shown in Figure c of Figure 8 ), and the degradation rate k value was obtained, as shown in Figure d of 7 Fe 2 Ti 2 O 17 Cl. The k value of the Ag-loaded sample (loading amount 5%) was 0.1938 min-1, which was 9.45 times that of the pure sample (Bi 7 Fe 2 Ti 2 O 17 Cl without Ag loading). It can be seen that Ag clusters significantly enhanced the photocatalytic activity of the Bi

[0079] 3. The above composite catalytic material was used for photocatalytic degradation of tetracycline hydrochloride (TCH), and the specific steps are as follows:

[0080] Its operation process was similar to that of degrading RhB. 5 mg of Ag / Bi 7 Fe 2 Ti 2 O 17 Cl was used to degrade 10 mg / L of TCH. The concentration of the TCH solution was measured using UV-vis. After 20 minutes of simulated visible light illumination, more than 80% of TCH could be degraded, and the results are as shown in Figure 9 and Table 1. Specifically, Figure 9 Figure (a) shows the UV absorption spectrum of the TCH solution. It can be seen that as the visible light illumination time prolongs, the UV absorption peak of the TCH solution weakens significantly, indicating that TCH is effectively degraded; as shown in Figure (b), based on the intensity of the UV absorption peak, quantitative analysis of TCH in the TCH solution was carried out. It was found that the degradation efficiency of TCH was relatively high in the first 5 minutes of visible light illumination, about 80% could be degraded in 10 minutes, and nearly 90% could be degraded in about 20 minutes.

[0081] 4. The above composite catalytic material was used for photocatalytic CO 2The reduction experiment was carried out as follows:

[0082] Weigh 50 mg of the composite photocatalytic material, disperse it evenly in absolute ethanol, then coat it on a glass slide, and place it in a 1 L reaction chamber. Then, introduce water in the form of steam into the reaction chamber, and subsequently introduce 1000 ppm of CO 2 . After the reaction chamber is stable, conduct the experiment in a closed loop, and the results are as Figure 10 shown. After 4 hours of reaction, the conversion amount of CO using the composite photocatalytic material is 3.25 μmol / g, which is 1.45 times that of the pure sample.

[0083] Example 2

[0084] Except that the molten salt is changed from sodium chloride and cesium chloride to potassium chloride and sodium chloride, the rest is the same as in Example 1. The results show that the same Bi 7 Fe 2 Ti 2 O 17 Cl photocatalytic material is obtained.

[0085] Example 3

[0086] Except that AgNO 3 is replaced by chloroauric acid or chloroplatinic acid, the rest is the same as in Example 1. The results show that similar Au or Pt nanoclusters to those in Example 1 are obtained.

[0087] Comparative Example 1

[0088] The operation is similar to that in Example 1, and the main difference is that in step 3, the hydrothermal method is used to prepare silver nanoclusters on the Bi 7 Fe 2 Ti 2 O 17 Cl ultrathin nanosheets. It is found that it is difficult to stably load metal nanoclusters on the Bi 7 Fe 2 Ti 2 O 17 Cl ultrathin nanosheets by the hydrothermal method.

[0089] In summary, the system design of the present invention has a simple process, uses all inexpensive and easily available materials, and is easy to recycle and can be reused, which conforms to the concept of green development; the bismuth-based oxohalide involved in the present invention has good photocatalytic degradation effect on organic dyes. Therefore, this system is worthy of being added to the renewable energy utilization system for further research to solve more problems in renewable energy utilization.

[0090] The specific embodiments described above further elaborate on the object, technical solution and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bismuth-based oxyhalide composite catalyst loaded with metal nanoclusters, characterized in that: The composite catalyst comprises: Bi7Fe2Ti2O 17 X thin nanosheets; and loaded on the Bi7Fe2Ti2O 17 Metal nanoclusters on X thin nanosheets, wherein X is at least one of Cl, Br and I, and the metal nanoclusters are one or more metals selected from Cu, Fe, Co, Ag, Pt, Pd, Bi, Au or Ag.

2. The composite catalyst according to claim 1, characterized in that: Based on the total mass of the composite catalyst, the loading amount of the metal nanoclusters is 0.1-10.0 wt%. 17 The size of the X thin nanosheets is 0.25 to 5 μm; and / or The metal nanoclusters are located in the Bi7Fe2Ti2O 17 The metal nanoclusters are stacked along the (020) crystal plane of the nanosheet, and the size of the metal nanoclusters is 0.1-20 nm.

3. A method for preparing a bismuth-based oxyhalide composite catalyst loaded with metal nanoclusters as claimed in claim 1 or 2, characterized in that: It includes the following steps: Bi2O3, Fe2O3, TiO2 and BiOX are used as precursor materials, where X = Cl, Br and / or I, and Bi7Fe2Ti2O is prepared by molten salt method or solid phase method. 17 X intrinsic material; For the Bi7Fe2Ti2O 17 The intrinsic material X is subjected to ultrasonic exfoliation or hydrothermal treatment to obtain Bi7Fe2Ti2O 17 X thin nanosheets; Under visible light, the Bi7Fe2Ti2O 17 The metal nanoclusters are uniformly deposited on the surface of the X thin nanosheets to obtain the composite catalyst; The metal nanoclusters are one or more metals selected from the group consisting of Cu, Fe, Co, Ag, Pt, Pd, Bi, Au and Ag.

4. The preparation method according to claim 3, characterized in that: Preparation of Bi7Fe2Ti2O by molten salt method 17 The operations of X intrinsic materials specifically include: Grinding and mixing the precursor material with a base molten salt according to a stoichiometric ratio, wherein the base molten salt is one or more of NaX, KX and CsX, and the mass ratio of the precursor material to the base molten salt is 1:(0-100); The ground and mixed mixture is calcined, and then repeatedly washed and dried to obtain the Bi7Fe2Ti2O 17 X intrinsic material, wherein the heating rate of the calcination treatment is 0.5-10°C / min, the calcination temperature is 500-900°C, and the calcination time is 5-20 h.

5. The preparation method according to claim 3, characterized in that: The conditions of the ultrasonic peeling include: ultrasonic frequency of 10-100 kHz, ultrasonic power of 50-1000W, ultrasonic duration of 1-100 h, and ultrasonic temperature of 20-60°C; The conditions of the hydrothermal treatment include: the hydrothermal solvent is one or more of water, ethanol, ethylene glycol, and glycerol, the hydrothermal temperature is 80-200° C., and the duration is 2-20 h.

6. The preparation method according to claim 3, characterized in that: By photodeposition method, the Bi7Fe2Ti2O 17 The uniform deposition of metal nanoclusters on the surface of X-thin nanosheets specifically includes: The Bi7Fe2Ti2O 17 The X thin nanosheets are mixed with a metal salt solution to obtain a mixed solution; The mixed solution is placed under a visible light source for reaction, and the composite catalyst is obtained after separation and drying.

7. The preparation method according to claim 6, characterized in that: The metal salt solution is a soluble salt solution of one or more metals selected from Cu, Fe, Co, Ag, Pt, Pd, Bi, Au or Ag.

8. The preparation method according to claim 6, characterized in that: The metal element of the metal salt and the Bi7Fe2Ti2O 17 The mass ratio of X thin nanosheets is (0.1~10):

100.

9. The preparation method according to claim 6, characterized in that: The reaction temperature is 20~40℃, and the reaction time is 5~30 min; The drying temperature is 50-100°C and the drying time is 1-15h.

10. Use of the bismuth-based oxyhalide composite catalyst loaded with metal nanoclusters as claimed in claim 1 or 2, or the bismuth-based oxyhalide composite catalyst loaded with metal nanoclusters obtained by the preparation method as claimed in any one of claims 3 to 9 in visible light catalytic reduction reaction of organic pollutants and carbon dioxide, wherein the organic pollutants include at least one of organic dyes or antibiotics.

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