Up-conversion luminescence modified BiOBr-based composite photocatalyst and preparation method thereof

Abstract

The invention discloses an up-conversion luminescence modified BiOBr-based composite photocatalyst and a preparation method thereof. The preparation method comprises the following steps: preparing a raw material A into an aqueous solution to obtain a turbid liquid; adding a polymer additive into the turbid liquid to obtain a precursor solution; putting the precursor solution into a hydrothermal reaction kettle for hydrothermal reaction to obtain white powder; centrifuging the white powder, washing and drying to obtain upconversion particles; fully and uniformly mixing the raw material B with up-conversion particles and ethylene glycol to obtain a turbid liquid; adding a polymer additive into the turbid liquid, fully and uniformly mixing to obtain a precursor solution, putting the precursor solution into a solvothermal reaction kettle to obtain powder, and centrifuging, washing and drying the powder to obtain the composite photocatalyst. The photocatalyst disclosed by the invention has a certain absorption effect on ultraviolet-visible-infrared band sunlight, so that the utilization efficiency of the photocatalyst on the sunlight is improved; the specific surface area is large, the adsorption capacity on pollutants is high, and degradation on the pollutants is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis, and in particular to an up-conversion luminescent modified BiOBr-based composite photocatalyst and a preparation method thereof. Background Art

[0002] Traditional photocatalytic materials, due to their low efficiency, are unable to address current environmental and energy challenges. Effective approaches to improving photocatalytic efficiency can be broadly divided into two categories: improving the internal structure of the photocatalytic material, thereby increasing the efficiency of electron-hole separation; and enhancing the photocatalytic material's ability to absorb light of different wavelengths.

[0003] Existing technologies typically improve catalytic efficiency by modifying the catalyst's structure, either by doping or creating heterojunctions, to enhance internal electron-hole separation. However, these methods offer limited optimization improvements to the solar absorption band, typically only absorbing sunlight in the ultraviolet and some visible wavelengths.

[0004] Furthermore, to further improve the efficiency of photocatalysts in utilizing sunlight, some researchers have combined upconversion luminescence with photocatalysis. This process converts low-energy light absorption into high-energy light, which is then absorbed and utilized by the photocatalytic material. This theoretically significantly increases the range of sunlight energy that can be utilized by the photocatalytic material, thereby improving the overall efficiency of photocatalysis. However, these methods often involve doping existing photocatalysts with rare earth elements to impart upconversion luminescence. However, this approach suffers from certain drawbacks in upconversion efficiency.

[0005] In order to solve the problem of photocatalyst efficiency itself, this patent invented a method of using high-efficiency upconversion particles and photocatalysts to obtain high-efficiency photocatalysts, which is of great significance to the optimization and improvement of photocatalysts. Summary of the Invention

[0006] The present invention aims to address the inherent efficiency issues of photocatalysts by providing an upconversion luminescent modified BiOBr-based composite photocatalyst and its preparation method. The process of the present invention offers advantages such as a wide absorption spectrum, high catalytic efficiency, universal applicability for pollutant degradation, and a simple and stable preparation method.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing an upconversion luminescent modified BiOBr-based composite photocatalyst comprises the following steps:

[0009] S1, preparing raw material A into an aqueous solution, and thoroughly mixing it in a polytetrafluoroethylene liner to obtain a suspension;

[0010] S2, adding a polymer additive to the suspension obtained in step S1 and mixing thoroughly to obtain a precursor solution;

[0011] S3, placing the precursor solution obtained in step S2 into a hydrothermal reactor and subjecting it to hydrothermal reaction for 24 hours to obtain a white powder;

[0012] S4, centrifuging, washing, and drying the white powder obtained in step S3 to obtain upconversion particles;

[0013] S5, mixing the raw material B (ammonium bromide, bismuth nitrate) and the upconversion particles obtained in step S4 with ethylene glycol to obtain a suspension;

[0014] S6, adding a polymer additive to the suspension obtained in step S5, and mixing thoroughly to obtain a precursor solution;

[0015] S7, placing the precursor solution obtained in step S6 into a solvent thermal reactor, and performing a solvent thermal reaction for 10 hours to obtain a powder;

[0016] S8, centrifuging, washing, and drying the powder obtained in step S7 to obtain the composite photocatalyst.

[0017] In step S1, the raw material A is sodium chloride, ammonium fluoride or rare earth element chloride; the rare earth element chloride is one of yttrium chloride, ytterbium chloride, erbium chloride and thulium chloride, or a mixture of two or more thereof.

[0018] In step S5, the raw material B is ammonium bromide or bismuth nitrate.

[0019] The washing treatment in steps S4 and S8 includes water washing and / or alcohol washing.

[0020] The polymer additive in steps S2 and S6 is polyvinyl pyrrolidone (PVP) or ethylenediaminetetraacetic acid (EDTA).

[0021] The polymer additive contained in steps S2 and S6 is one of PVP and EDTA, and its mass accounts for 20%-30% of the mass of raw materials A and B in steps S1 and S5.

[0022] In steps S2 and S7, the solvent thermal temperature is 120-220°C;

[0023] In steps S4 and S8, the drying temperature is 80° C. and the drying time is 12 h.

[0024] The mass of the rare earth element chloride accounts for 1%-20% of the mass of the raw material.

[0025] An up-conversion luminescent modified BiOBr-based composite photocatalyst is obtained by the above preparation method.

[0026] Compared with the prior art, the present invention has the following advantages and effects:

[0027] (1) The photocatalyst of the present invention has a certain degree of absorption effect on sunlight in the ultraviolet, visible and infrared bands, thereby improving the efficiency of the photocatalyst in utilizing sunlight.

[0028] (2) The photocatalyst of the present invention has a large specific surface area and a strong adsorption capacity for pollutants, which helps to degrade the pollutants.

[0029] (3) The photocatalyst of the present invention has the ability to degrade most organic pollutants such as rhodamine B, methylene blue, and methyl orange.

[0030] (4) The photocatalyst of the present invention is stable in nature, and the catalytic performance does not decrease significantly after multiple cycles.

[0031] (5) The photocatalyst of the present invention is non-toxic and harmless and does not cause secondary pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the upconversion luminescence spectrum of the upconversion particles claimed in the present invention.

[0033] Figure 2 This is a scanning electron microscope image of the photocatalyst of the present invention.

[0034] Figure 3 The UV-Vis-NIR diffuse reflectance spectrum of the sample of the present invention is shown in Figure 2. As can be seen, compared with pure BiOBr, the composite photocatalyst has an additional absorption peak at 980nm, indicating that the composite photocatalyst responds in the near-infrared band.

[0035] Figure 4 This is the upconversion luminescence spectrum of the sample claimed in the present invention. It can be seen that the composite photocatalyst has similar upconversion luminescence performance to NaYF4. Under 980nm laser irradiation, it can release light with lower wavelength and higher energy to excite BiOBr for photocatalysis.

[0036] Figure 5 This is a diagram showing the degradation effect of the photocatalyst of the present invention on Rhodamine B.

[0037] Figure 6 It is a diagram of the catalytic principle of the photocatalyst described in the present invention. DETAILED DESCRIPTION

[0038] The present invention is described in further detail below with reference to specific embodiments.

[0039] Example 1

[0040] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of erbium trichloride aqueous solution (0.8 M), 225 μl of thulium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0041] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0042] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0043] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles NI;

[0044] Example 2

[0045] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of thulium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0046] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0047] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0048] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles NII;

[0049] Example 3

[0050] (1) 10 ml of sodium chloride ethylene glycol solution (0.3 M), 10 ml of ammonium fluoride ethylene glycol solution (2.5 M), 440 μl of yttrium trichloride solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of thulium trichloride aqueous solution (0.15 M), and 40 ml of ethylene glycol were thoroughly mixed in a polytetrafluoroethylene liner;

[0051] (2) Add 0.3 g PVP to the homogeneous suspension of step (1) and mix thoroughly;

[0052] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0053] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles NIII;

[0054] Example 4

[0055] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of erbium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0056] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0057] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0058] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles NIV;

[0059] Depend on Figure 1 It can be seen that the upconversion luminescence properties of the four upconversion particles vary, indicating that the type of doping element, solvent, and surfactant all have a significant impact on the performance of NaYF4. Among them, NI has the worst performance, indicating that the formulation doped with erbium trichloride and thulium trichloride is not desirable. The overall luminescence intensity of NIII is weak, indicating that the formulation using ethylene glycol as the solvent and PVP as the surfactant is not desirable. Compared with NIII, NIV has a shorter overall luminescence wavelength and greater energy, which is more conducive to the absorption and utilization of the photocatalyst. Therefore, the preparation formulation doped with ytterbium trichloride and erbium trichloride, using deionized water as the solvent and EDTA as the surfactant was selected.

[0060] Example 5

[0061] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of erbium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0062] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0063] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0064] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles;

[0065] (5) 5 mmol of ammonium bromide, 5 mmol of bismuth nitrate, and 0.075 g of the upconversion particles obtained in step (4) were thoroughly mixed in 50 ml of ethylene glycol and transferred to a polytetrafluoroethylene liner;

[0066] (6) Add 0.1 g of PEI to the homogeneous suspension of step (5) and mix thoroughly;

[0067] (7) placing the precursor solution obtained in step (6) into a solvent thermal reactor and subjecting it to a solvent thermal reaction at 120° C. for 10 hours;

[0068] (8) The particles obtained in step (7) are centrifuged, washed, and dried to obtain Example 5.

[0069] Example 6

[0070] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of erbium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0071] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0072] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0073] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles;

[0074] (5) 5 mmol of ammonium bromide, 5 mmol of bismuth nitrate, and 0.075 g of the upconversion particles obtained in step (4) were thoroughly mixed in 50 ml of ethylene glycol and transferred to a polytetrafluoroethylene liner;

[0075] (6) Add 0.1 g of PEI to the homogeneous suspension of step (5) and mix thoroughly;

[0076] (7) placing the precursor solution obtained in step (6) into a solvent thermal reactor and subjecting it to a solvent thermal reaction at 160° C. for 10 hours;

[0077] (8) The particles obtained in step (7) are centrifuged, washed, and dried to obtain Example 6.

[0078] Example 7

[0079] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of erbium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0080] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0081] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0082] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles;

[0083] (5) 2.5 mmol of ammonium bromide, 2.5 mmol of bismuth nitrate, and 0.075 g of the upconversion particles obtained in step (4) were thoroughly mixed in 50 ml of ethylene glycol and transferred to a polytetrafluoroethylene liner;

[0084] (6) Add 0.1 g PVP to the homogeneous suspension of step (5) and mix thoroughly;

[0085] (7) placing the precursor solution obtained in step (6) into a solvent thermal reactor and subjecting it to a solvent thermal reaction at 120° C. for 10 hours;

[0086] (8) The particles obtained in step (7) are centrifuged, washed, and dried to obtain Example 7.

[0087] Example 8

[0088] (1) 10 ml of sodium chloride aqueous solution (0.3 M), 10 ml of ammonium fluoride aqueous solution (2.5 M), 440 μl of yttrium trichloride aqueous solution (2.7 M), 375 μl of ytterbium trichloride aqueous solution (0.8 M), 225 μl of erbium trichloride aqueous solution (0.15 M), and 40 ml of deionized water were thoroughly mixed in a polytetrafluoroethylene liner;

[0089] (2) Add 0.3 g of EDTA to the homogeneous suspension of step (1) and mix thoroughly;

[0090] (3) placing the precursor solution obtained in step (2) into a hydrothermal reactor and subjecting it to a hydrothermal reaction at 180° C. for 20 hours;

[0091] (4) centrifuging, washing, and drying the particles obtained in step (3) to obtain upconversion particles;

[0092] (5) 2.5 mmol of ammonium bromide, 2.5 mmol of bismuth nitrate, and 0.075 g of the upconversion particles obtained in step (4) were thoroughly mixed in 50 ml of ethylene glycol and transferred to a polytetrafluoroethylene liner;

[0093] (6) Add 0.1 g PVP to the homogeneous suspension of step (5) and mix thoroughly;

[0094] (7) placing the precursor solution obtained in step (6) into a solvent thermal reactor and subjecting it to a solvent thermal reaction at 160° C. for 10 hours;

[0095] (8) The particles obtained in step (7) are centrifuged, washed, and dried to obtain Example 8.

[0096] The performance test results of Examples 5-8 are shown in Table 1.

[0097] The test conditions are as follows: 50mg of photocatalyst is dissolved in 50ml of a pollutant solution with a concentration of 10mg / l, and a 300W xenon lamp (which filters out ultraviolet light below 420nm and retains visible-infrared light) is used as the light source for degradation testing.

[0098] Table 1 Photocatalyst performance test results

[0099]

[0100] As described above, the present invention can be implemented better.

[0101] Compared with traditional powders, the photocatalyst of the present invention has a certain degree of absorption effect on sunlight in the ultraviolet, visible and infrared bands, thereby improving the efficiency of the photocatalyst in utilizing sunlight; it has a large specific surface area and a strong adsorption capacity for pollutants, which helps to degrade pollutants; it has the ability to degrade most organic pollutants such as rhodamine B, methylene blue, and methyl orange; it has stable properties, and the catalytic performance does not decrease significantly after multiple cycles; it is non-toxic and harmless, and does not cause secondary pollution to the environment.

[0102] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing an upconversion luminescence modified BiOBr-based composite photocatalyst, characterized in that: The following steps are involved: S1, preparing raw material A into an aqueous solution, and thoroughly mixing it in a polytetrafluoroethylene liner to obtain a suspension; S2, adding a polymer additive to the suspension obtained in step S1 and mixing thoroughly to obtain a precursor solution; S3, placing the precursor solution obtained in step S2 into a hydrothermal reactor and subjecting it to hydrothermal reaction for 24 hours to obtain a white powder; S4, centrifuging, washing, and drying the white powder obtained in step S3 to obtain upconversion particles; S5, mixing the raw material B and the upconversion particles obtained in step S4 with ethylene glycol to obtain a suspension; S6, adding a polymer additive to the suspension obtained in step S5, and mixing thoroughly to obtain a precursor solution; S7, placing the precursor solution obtained in step S6 into a solvent thermal reactor, and performing a solvent thermal reaction for 10 hours to obtain a powder; S8, centrifuging, washing, and drying the powder obtained in step S7 to obtain the composite photocatalyst.

2. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 1, characterized in that: In step S1, the raw material A is sodium chloride, ammonium fluoride or rare earth element chloride.

3. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 2, characterized in that: The rare earth element chloride is one of yttrium chloride, ytterbium chloride, erbium chloride, and thulium chloride, or a mixture of two or more thereof.

4. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 2, characterized in that: In step S5, the raw material B is ammonium bromide or bismuth nitrate.

5. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 1, characterized in that: The washing treatment in steps S4 and S8 includes water washing and / or alcohol washing.

6. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 1, characterized in that: The polymer additive in steps S2 and S6 is polyvinyl pyrrolidone (PVP) or ethylenediaminetetraacetic acid.

7. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 1, characterized in that: The polymer additive included in steps S2 and S6 is one of PVP and EDTA, and its mass accounts for 20%-30% of the mass of the raw materials A and B in steps S1 and S5.

8. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 1, characterized in that: In steps S2 and S7, the solvent thermal temperature is 120-220°C.

9. The method for preparing the upconversion luminescence modified BiOBr-based composite photocatalyst according to claim 1, characterized in that: In steps S4 and S8, the drying temperature is 80° C. and the drying time is 12 hours.

10. An upconversion luminescence modified BiOBr-based composite photocatalyst, characterized in that Obtained by the preparation method according to any one of claims 1 to 9.

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