Preparation method, product and application of t-Se / ZnO composite nano heterojunction particles

Abstract

The invention relates to the technical field of photocatalytic nano materials, in particular to a preparation method, a product and application of t-Se / ZnO composite nano heterojunction particles. The preparation method comprises the following steps: dissolving a selenium-containing compound and a dispersing agent in water, then adding ZnO nano-particles, and uniformly dispersing to obtain a turbid liquid; adding a reducing agent solution into the turbid liquid to carry out reduction reaction, and then standing, centrifuging and washing to obtain alpha-Se / ZnO particles; and dispersing the alpha-Se / ZnO particles in an organic solvent, aging, centrifuging, washing and drying to obtain the t-Se / ZnO composite nano heterojunction particles. The catalyst is prepared in one pot by utilizing a mild water phase reduction method, only normal-temperature reaction and normal-temperature aging are needed, and the process is simple. The t-Se / ZnO composite nano heterojunction particle disclosed by the invention is a visible light catalytic degradation material with excellent performance, and has good photocatalytic degradation performance on organic pollutants.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytic nanomaterials, and in particular to a preparation method, product and application of t-Se / ZnO composite nano heterojunction particles. Background Art

[0002] As an important group VI element semiconductor, the band gap width of Se is only 1.56 eV, and it has excellent visible light responsiveness. t-Se is the most stable element among many Se allotropes, containing an infinite chain of covalently bonded Se atoms arranged in a spiral shape. The spiral chain is combined in a triangle by van der Waals forces in the hexagonal lattice. Therefore, a single t-Se has a one-dimensional growth trend along the c-axis. In 2011, Hsu et al. first paid attention to the photocatalytic performance of Se and found that Se nanorods (t-Se NRs) had a significant effect on the degradation of methylene blue under a dark field environment after a short period of ultraviolet light. With the help of the co-catalyst H2O2, t-Se NRs can quickly degrade methyl orange under visible light, showing its application potential as an elemental semiconductor photocatalyst. However, in the absence of a co-catalyst, the efficiency of single t-Se NRs in degrading dyes under visible light needs to be improved. Summary of the invention

[0003] Based on the above content, the present invention provides a preparation method, product and application of t-Se / ZnO composite nano heterojunction particles.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention is a method for preparing t-Se / ZnO composite nano heterojunction particles, comprising the following steps:

[0006] The selenium-containing compound and the dispersant are dissolved in water, and then ZnO nanoparticles are added and dispersed evenly to obtain a suspension;

[0007] Adding a reducing agent solution to the suspension to perform a reduction reaction, then standing, centrifuging, and washing to obtain α-Se / ZnO particles;

[0008] The α-Se / ZnO particles are dispersed in an organic solvent, aged, centrifuged, washed and dried to obtain the t-Se / ZnO composite nano heterojunction particles.

[0009] The second technical solution of the present invention is a t-Se / ZnO composite nano heterojunction particle prepared according to the above-mentioned preparation method.

[0010] The third technical solution of the present invention is the application of the above-mentioned t-Se / ZnO composite nano heterojunction particles in the photocatalytic degradation of organic pollutants.

[0011] The present invention discloses the following technical effects:

[0012] The preparation process of the present invention is simple and the raw materials are easily available. The t-Se / ZnO composite nanoheterojunction particles of the present invention are prepared by a one-pot method using a mild aqueous phase reduction method, and only room temperature reaction and room temperature aging are required.

[0013] As shown by high-resolution transmission electron microscopy, the t-Se / ZnO composite nanoheterojunction particles of the present invention have obvious crystal phase partitioning. The hetero-junction particles are composed of one-dimensional hexagonal t-Se nanorods and hexagonal ZnO nanoparticles with irregular morphology. The diameter of the t-Se rods is 50-150 nm, and the ZnO particles are 20-40 nm.

[0014] The t-Se / ZnO composite nanoheterojunction particles of the present invention are a visible light catalytic degradation material with excellent performance. Under the irradiation of a 300W xenon lamp, complete decolorization of RhB can be achieved within 3h, and the degradation rate reaches more than 97%. Compared with the separate Se or ZnO, the visible light catalytic degradation rate is greatly improved, and the formation of a hetero-junction between the two significantly improves their visible light catalytic performance. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 For the adsorption-degradation performance curves of t-Se / ZnO composite nanoheterojunction particles in Examples 1-4, t-Se nanorods in Example 5, commercial Se, and nano-ZnO under visible light (420nm ≤ λ ≤ 780nm, 300W xenon lamp);

[0017] Figure 2 For the pseudo-first-order kinetics of the visible light degradation of RhB by the t-Se / ZnO composite nanoheterojunction particles in Example 1 and its k value (min -1 )

[0018] Figure 3 For the X-ray diffraction (XRD) pattern of the t-Se nanorods in Example 5;

[0019] Figure 4Scanning electron microscope (SEM) images (a)-(e) and transmission electron microscope (TEM) image (f) of t-Se / ZnO composite nanoheterojunction particles with different ZnO contents prepared in Examples 1-4 and t-Se nanorods in Example 5; wherein, (a) t-Se / ZnO (80 wt%); (b) t-Se / ZnO (60 wt%); (c) t-Se / ZnO (40 wt%); (d) t-Se / ZnO (20 wt%); (e), (f) t-Se;

[0020] Figure 5 TEM image and high-resolution transmission electron microscope (HRTEM) image of t-Se / ZnO (80 wt%) particles in Example 1;

[0021] Figure 6 Schematic diagram of the visible-light catalytic mechanism of the t-Se / ZnO composite nanoheterojunction in the present invention. Detailed implementation manners

[0022] The various exemplary implementation manners of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing particular implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0025] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0026] The terms "comprising", "including", "having", "containing", etc. used in this text are all open-ended terms, meaning including but not limited to.

[0027] "Normal temperature" as described in the present invention, unless otherwise specified, all represents 20 - 35 °C.

[0028] At present, there are relatively few studies on the preparation and performance of photocatalysts of semiconductor composite heterojunction materials containing t-Se. ZnO has a relatively wide bandgap width (about 3.2 eV), similar to TiO2, and when used alone, the utilization efficiency of sunlight is relatively low. Compared with traditional TiO2 photocatalytic materials, in addition to being simple to prepare, safe and non-toxic, ZnO is cheaper and has better effects in photocatalytic degradation and photoelectric conversion. Therefore, ZnO has gradually become a better alternative material for TiO2. Therefore, the present invention selects the semiconductor ZnO, which has good photocatalytic activity only under ultraviolet light, as another component. While synthesizing t-Se that can effectively absorb visible light by chemical reduction method at normal temperature, nano-sized ZnO particles are in-situ compounded on t-Se, and the degradation rate of Rhodamine B (RhB) by the t-Se / ZnO composite under visible light is tested. It is found that the sample after compounding has a significant improvement compared with the single-component sample. The specific method is to disperse the visible light photocatalytic material at a concentration of 50 - 100 mg / L in an aqueous solution of RhB at a concentration of 10 mg / L. The container used is a quartz beaker, which is placed in a dark box. Under magnetic stirring at 350 rpm for 60 min, the adsorption-desorption equilibrium between the catalyst and RhB molecules is achieved, and then the visible light degradation process of RhB is carried out by turning on a xenon lamp to simulate sunlight. The results show that commercial Se, t-Se, and ZnO all have visible light photocatalytic degradation effects on RhB. Especially, the product performance of the t-Se / ZnO composite nanoheterojunction particles is greatly improved compared with the single Se or ZnO material, and the time to complete decolorization is within 3 h.

[0029] The present invention successfully prepares heterojunction particles composed of hexagonal t-Se crystals and hexagonal ZnO crystals by a mild preparation method. Its morphology presents one-dimensional t-Se nanorods and irregular ZnO nanoparticles. The diameter of the t-Se rods is 50 - 150 nm, and the ZnO particles are 20 - 40 nm. Its photocatalytic performance has achieved better effects compared with the prior art, and the photocatalytic performance has been significantly improved compared with the single-component Se or ZnO. This material realizes the effective decolorization treatment of the dye RhB under visible light, and the complete decolorization of RhB can be achieved within 3 h under visible light irradiation, and the degradation rate reaches more than 97%. The t-Se / ZnO composite nanoheterojunction particles provided by the present invention are a visible light catalytic degradation material with excellent performance.

[0030] The first aspect of the present invention provides a preparation method of t-Se / ZnO composite nanoheterojunction particles, comprising the following steps:

[0031] Dissolve the selenium-containing compound and the dispersant in water, and then add ZnO nanoparticles and disperse them evenly to obtain a suspension;

[0032] Add a reducing agent solution to the suspension for a reduction reaction, and then let it stand, centrifuge, wash to obtain α-Se / ZnO particles;

[0033] Disperse the α-Se / ZnO particles in an organic solvent, age, centrifuge, wash, and dry to obtain the t-Se / ZnO composite nanoheterojunction particles.

[0034] In a preferred embodiment of the present invention, the selenium-containing compound is at least one of selenium dioxide, sodium selenite, and potassium selenite; preferably selenium dioxide and sodium selenite, and more preferably sodium selenite.

[0035] The dispersant is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and β-cyclodextrin; preferably cetyltrimethylammonium bromide and β-cyclodextrin, and more preferably β-cyclodextrin.

[0036] The reducing agent in the reducing agent solution is at least one of ascorbic acid, glucose, and sodium formaldehyde sulfoxylate, and the solvent is water; preferably ascorbic acid and glucose, and more preferably ascorbic acid.

[0037] When adding the reducing agent solution to the suspension, it needs to be added quickly. If the reducing agent is added slowly, it will result in a small number and large size of α-Se particles formed in a short period, which will affect the crystallization rate of t-Se during aging.

[0038] The method of dispersing evenly is ultrasonic dispersion and stirring.

[0039] In a preferred embodiment of the present invention, the mass ratio of selenium element in the selenium-containing compound to the ZnO nanoparticles is 1:9 to 10:0.

[0040] The concentration of the selenium-containing compound in the suspension is 0.01 to 0.05 mol / L, and more preferably 0.03 mol / L.

[0041] The higher the concentration of the selenium-containing compound in the suspension, the poorer the dispersibility of the formed alpha selenium particles and the larger the particle size; therefore, the present invention preferably limits the concentration of the selenium-containing compound in the suspension to 0.01 to 0.05 mol / L.

[0042] The present invention does not make a special limitation on the addition amount of the dispersant, and the amount of the dispersant can make the selenium-containing compound fully dispersed evenly.

[0043] In the present invention, the dosage of the reducing agent cannot exceed the stoichiometric ratio in the reduction reaction equation. For example, the stoichiometric ratio of ascorbic acid to selenious acid is 2:1 (the reaction equation is as follows). When ascorbic acid is in excess, ZnO will dissolve. For example, when the molar ratio of ascorbic acid to selenious acid is 4:1, ZnO completely dissolves.

[0044] H2SeO3+2C6H8O6→Se↓+2C6H6O6+3H2O

[0045] In a preferred embodiment of the present invention, the temperature of the reduction reaction is 20-70 °C and the time is 1-8 h; preferably 25-50 °C, 2-4 h, and more preferably 25 °C, 4 h.

[0046] In a preferred embodiment, the reduction reaction is carried out under stirring, that is, at least one of magnetic stirring and mechanical stirring, and the stirring rate is 300-1000 rpm. Preferably, it is magnetic stirring, and the stirring rate is 200-600 rpm, and more preferably 600 rpm.

[0047] In a preferred embodiment, the standing time of the reduction product is 0.5-2 h, preferably 0.5-1 h, and more preferably 0.5 h.

[0048] In a preferred embodiment, the centrifugation is carried out using a high-speed centrifuge, with a centrifugation speed of 3000-12000 rpm and a centrifugation time of 5-30 min. Preferably, it is 8000-10000 rpm, 5-10 min, and more preferably 10000 rpm, 5 min.

[0049] In a preferred embodiment of the present invention, the organic solvent is at least one of absolute ethanol, absolute methanol, acetone, and pyridine; preferably absolute ethanol and acetone, and more preferably absolute ethanol.

[0050] In a preferred embodiment of the present invention, the aging temperature is 20-35 °C and the time is 1-48 h; further preferably, 25-30 °C, 12-24 h, and more preferably 25 °C, 24 h.

[0051] In a preferred embodiment of the present invention, stirring is also carried out before aging to make the α-Se / ZnO particles disperse evenly. The stirring time is 10-30 min, the stirring rate is 100-1000 rpm, and the stirring temperature is 20-35 °C. Preferably, it is 20-30 min, 200-600 rpm, 25-30 °C, and more preferably 30 min, 600 rpm, 25 °C. Subsequently, no stirring is required during aging, and aging is carried out in a static state.

[0052] The reason for the aging step in the present invention is:

[0053] The selenium-containing compound is decomposed into elemental selenium by a reducing agent to form amorphous α-Se particles. The phase transition energy for α-Se to transform into t-Se is very low, only 6.63 kJ / mol. Therefore, α-Se is also unstable at room temperature. As long as a certain driving force such as ultrasound, catalyst, or organic solvent is applied, it will age to form seeds of triangular selenium, and then the triangular selenium grows anisotropically along one dimension to form t-Se hexagonal crystals, accompanied by the re-dissolution of the amorphous α-Se to be transformed into t-Se crystals. The formation of t-Se ensures that it is in a stable semiconductor crystal state. t-Se has a relatively narrow bandgap (1.56 eV) and excellent visible light responsiveness, making it suitable for the field of photocatalysis.

[0054] The drying method is at least one of constant temperature drying, vacuum drying, and freeze drying; among them, the constant temperature or vacuum drying temperature is 50 - 80 °C, and the drying time is 12 - 48 h. Preferably, it is vacuum drying, the drying temperature is 50 - 60 °C, and the drying time is 12 - 24 h. More preferably, it is 50 °C and 24 h.

[0055] The second aspect of the present invention provides t-Se / ZnO composite nanoheterojunction particles prepared by the above-mentioned preparation method.

[0056] The third aspect of the present invention provides the application of the above-mentioned t-Se / ZnO composite nanoheterojunction particles in the photocatalytic degradation of organic pollutants.

[0057] The t-Se / ZnO composite nanoheterojunction particles are composed of one-dimensional t-Se nanorods and irregular ZnO nanoparticles. The diameter of the t-Se rods is 50 - 150 nm, and the ZnO particles are 20 - 40 nm. It can be clearly seen from the high-resolution transmission electron microscope that the heterojunction is composed of two significantly different crystal phases. 0.21 nm and 0.25 nm respectively correspond to the interplanar spacings of the (102) plane of t-Se and the (101) plane of ZnO.

[0058] In a preferred embodiment of the present invention, the organic pollutant is at least one of methylene blue, methyl orange, rhodamine B, 2,4-diphenol, and tetracycline.

[0059] The t-Se / ZnO composite nanoheterojunction particles provided by the present invention can completely decolorize the cationic dye RhB within 3 h under a 300 W xenon lamp (420 - 780 nm), and the degradation rate reaches more than 97%.

[0060] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art. The reagents, raw materials, or equipment used, unless otherwise specified, are all purchased from commercial channels or have been made public.

[0061] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] Step 1: In a 25 mL round-bottom flask, add 0.05 g of sodium selenite and 0.05 g of β-cyclodextrin, add 10 mL of deionized water, and stir until completely dissolved; add 0.0913 g of ZnO nanoparticles, and ultrasonically disperse them evenly to form a milky white suspension; additionally weigh 0.0493 g of ascorbic acid, add 10 mL of deionized water to prepare a solution; under strong stirring, quickly add the ascorbic acid aqueous solution to the milky white suspension, and carry out a reduction reaction at room temperature for 4 h. After the reaction is completed, let it stand for 0.5 h to form a precipitate. Centrifuge the precipitate at 10000 rpm for 5 min, and wash it 3 times with deionized water and anhydrous ethanol respectively to obtain α-Se / ZnO particles as the product.

[0064] Step 2: In a 25 mL round-bottom flask, disperse the α-Se / ZnO particles in 20 mL of anhydrous ethanol, keep it away from light, and let it age at room temperature for 24 h. The brick-red α-Se nanoparticles in the product gradually transform into black t-Se nanorods, and the color of the precipitate gradually deepens. After aging is completed, centrifuge the precipitate at 10000 rpm for 5 min, and wash it 3 times with deionized water and anhydrous ethanol respectively. Place the product in an oven and dry it under vacuum at 50 °C for 24 h to obtain t-Se / ZnO composite nanoheterojunction particles with a ZnO content of 80 wt% (abbreviation: t-Se / ZnO).

[0065] Example 2

[0066] The difference from Example 1 is only that the addition amount of ZnO nanoparticles is 0.0342 g; t-Se / ZnO composite nanoheterojunction particles with a ZnO content of 60 wt% are prepared.

[0067] Example 3

[0068] The difference from Example 1 is only that the addition amount of ZnO nanoparticles is 0.0152 g; t-Se / ZnO composite nanoheterojunction particles with a ZnO content of 40 wt% are prepared.

[0069] Example 4

[0070] The difference from Example 1 is only that the addition amount of ZnO nanoparticles is 0.0057 g; t-Se / ZnO composite nanoheterojunction particles with a ZnO content of 20 wt% are prepared.

[0071] Example 5

[0072] It is different from Example 1 only in that the addition of ZnO nanoparticles is omitted; t-Se nanorods are prepared.

[0073] The samples prepared in Examples 1 to 5 were characterized, and the results are as follows:

[0074] Figure 3 It is the X-ray diffraction (XRD) pattern of the t-Se nanorods in Example 5. As Figure 3 shown, the peak shape of t-Se is sharp and the crystallization is good, which matches well with the standard card PDF#06-0362, belonging to the hexagonal crystal system, and its unit cell parameters are α = β = 90°, γ = 120°, and no SeO2 and other impurity phases are observed. Pure t-Se elemental substance can be obtained by the liquid-phase reduction method at room temperature. t-Se is the most stable allotrope of selenium element and is easy to combine with different photocatalyst semiconductors without affecting the original visible light responsiveness of the Se elemental substance.

[0075] Figure 4 They are the scanning electron microscope images (80000×) and transmission electron microscope images (30000×) of t-Se / ZnO and t-Se nanorods. It can be seen that the single t-Se prepared by the chemical reduction method presents an ultra-long rod-like structure ( Figure 4 (e) and (f) in it), and it is easy for the long rods to form bundles. When a large amount of nano-ZnO is added to compound with t-Se, the reduction product t-Se elemental substance is greatly affected by the original morphology of nano-ZnO and basically does not form ultra-long rods ( Figure 4 (a) and (b) in it); when the amount of ZnO is reduced to 40 wt%, the t-Se / ZnO composite forms an interconnected worm-like structure ( Figure 4 (c) in it); when the amount of ZnO is reduced to 20 wt%, the reduction product t-Se is basically not affected by nano-ZnO and retains the original ultra-long rod-like morphology of t-Se, and some nano-ZnO particles adhere to it ( Figure 4 (d) in it).

[0076] Figure 5 They are the transmission electron microscope image of the t-Se / ZnO (80 wt%) heterojunction in Example 1 magnified 30000 times and the high-resolution transmission electron microscope image of 800000. It can be seen that the t-Se / ZnO heterojunction is composed of hexagonal t-Se and hexagonal ZnO particles, and it can be clearly seen that there are two significantly different crystal planes on the particles. Among them, the interplanar spacing of the (102) crystal plane of t-Se is 0.21 nm, and the interplanar spacing of the (101) crystal plane of ZnO is 0.25 nm, which is consistent with the characteristic diffraction peaks shown in the XRD pattern.

[0077] Figure 6It is a schematic diagram of the visible-light catalytic mechanism of t-Se / ZnO composite nanoheterojunction particles in the examples. The band edge potentials of the hexagonal t-Se nanorods are -0.5 eV and 1.06 eV respectively, and the narrow band gap (1.56 eV) can effectively absorb electromagnetic waves in the visible band. The band edge potentials of hexagonal ZnO are -0.31 eV and 2.98 eV respectively, and it can only effectively absorb electromagnetic waves in the ultraviolet band. When the t-Se / ZnO composite nanoheterojunction particles are irradiated with visible light, both t-Se and ZnO generate electron-hole pairs (e - -h + ). The photoinduced electrons can immediately break free from the constraints of the defect state, leaving positively charged holes. The migration rate of photogenerated electrons from t-Se to ZnO is faster than the hole migration from ZnO to t-Se. That is to say, when visible light irradiates t-Se / ZnO, the photogenerated electrons are collected earlier and quickly transferred from t-Se to ZnO, thereby increasing the utilization rate of visible light energy by ZnO and reducing the recombination between photogenerated carriers. It is precisely due to the introduction of the ZnO component to form a heterojunction that a large number of photogenerated electrons and holes can be prevented from recombining, thereby improving the photocatalytic activity of the material.

[0078] Effect verification example

[0079] Adsorption test: Taking the dye RhB as an example, the photocatalytic activities of materials such as t-Se / ZnO (80 wt%), t-Se / ZnO (60 wt%), t-Se / ZnO (40 wt%), t-Se / ZnO (20 wt%), and t-Se nanorods in Examples 1-5 were studied as catalyst samples. The dye degradation was carried out with magnetic stirring at 350 rpm in a 100 mL quartz beaker. Usually, 50 mg of the catalyst sample was dispersed into 100 mL of an aqueous RhB solution (concentration 10 mg / L). Dark adsorption was carried out for 60 min before irradiation. 1 mL of the suspension was taken out every 10-20 min, centrifuged at 10000 rpm for 5 min, and the photocatalyst particles were removed with a 0.22 μm filter head. The absorbance of RhB at 554 nm was measured with a UV-visible spectrophotometer. When the absorbance no longer decreased, it indicated that the adsorption-desorption equilibrium had been reached.

[0080] Visible-light degradation test: The photocatalytic activities of the prepared samples were evaluated by simulating the degradation of the RhB solution under sunlight irradiation with a xenon lamp. In the photocatalytic experiment, a 300 W xenon lamp was used as the visible-light source (a UV filter of 200-420 nm was added, and the light source wavelength range was 420 nm ≤ λ ≤ 780 nm). At certain time intervals, 1 mL of the suspension was collected and centrifuged at 10000 rpm for 5 min, and the photocatalyst particles were removed with a 0.22 μm filter head. Then, the change in the maximum absorption peak of RhB at 554 nm was recorded with a UV-visible spectrophotometer to analyze the degradation degree of the filtrate.

[0081] As Figures 1 - 2 shown, after adding t-Se / ZnO composite nano-heterojunction particles, the change in the degradation rate of RhB under visible light (420 - 780 nm) irradiation in the first 180 min basically conforms to the pseudo-first-order kinetic equation, and the degradation rate (k value) is 0.0205 min -1 . Measuring the absorbance of the degradation product at the characteristic absorption peak of RhB at 554 nm, it is obtained that the degradation rate reaches 97.19% at 180 min of visible light irradiation (t-Se / ZnO (80 wt%) in Example 1), which is significantly higher than that of single-component photocatalysts such as commercial Se powder (particle size 75 μm, black powder), t-Se nanorods, and nano-ZnO (particle size 20 - 40 nm). It shows that compounding with other semiconductors to prepare a heterojunction containing elemental t-Se is an effective measure to improve its photocatalytic activity. As Figure 1 shown, when the zinc oxide content is 60 wt% and 40 wt%, the degradation rates of RhB under visible light irradiation for 180 min are 78.37% and 75.64% respectively. As the zinc oxide content increases, the degradation rate of the prepared product for RhB under visible light irradiation for 180 min gradually increases.

[0082] In summary, while synthesizing t-Se by aqueous-phase chemical reduction at room temperature, composite nano-scale ZnO particles are formed on it, and the degradation rate of RhB by the Se / ZnO composite under visible light is tested. It is found that the composite sample has a significant improvement compared with single-component photocatalysts such as commercial Se powder, t-Se nanorods, and nano-ZnO. The xenon lamp simulation sunlight test shows that a degradation rate of more than 97% can be achieved within 3 h of visible light irradiation, and the maximum degradation rate k value in the first 3 h is 0.0205 min -1 . This shows that compounding t-Se with other semiconductors with matching energy levels to form a heterojunction to reduce the recombination of photo-generated electrons and photo-generated holes can significantly improve the photocatalytic activity of elemental t-Se itself.

[0083] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing t-Se / ZnO composite nano heterojunction particles, characterized in that: The following steps are involved: The selenium-containing compound and the dispersant are dissolved in water, and then ZnO nanoparticles are added and dispersed evenly to obtain a suspension; Adding a reducing agent solution to the suspension to perform a reduction reaction, then standing, centrifuging, and washing to obtain α-Se / ZnO particles; The α-Se / ZnO particles are dispersed in an organic solvent, aged, centrifuged, washed and dried to obtain the t-Se / ZnO composite nano heterojunction particles.

2. The preparation method according to claim 1, characterized in that: The selenium-containing compound is at least one of selenium dioxide, sodium selenite, and potassium selenite; The dispersant is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and β-cyclodextrin; The reducing agent in the reducing agent solution is at least one of ascorbic acid, glucose and sodium formaldehyde sulfoxylate, and the solvent is water.

3. The preparation method according to claim 1, characterized in that: The mass ratio of selenium element in the selenium-containing compound to the ZnO nanoparticles is 1:9-10:

0.

4. The preparation method according to claim 1, characterized in that: The reduction reaction is carried out at a temperature of 20 to 70° C. and for a time of 1 to 8 hours.

5. The preparation method according to claim 1, characterized in that: The organic solvent is at least one of anhydrous ethanol, anhydrous methanol, acetone and pyridine.

6. The preparation method according to claim 1, characterized in that: The aging temperature is 20-35° C. and the aging time is 1-48 hours.

7. t-Se / ZnO composite nano heterojunction particles prepared according to the preparation method according to any one of claims 1 to 6.

8. Use of the t-Se / ZnO composite nano heterojunction particles as claimed in claim 7 in photocatalytic degradation of organic pollutants.

9. The use according to claim 8, characterized in that: The organic pollutant is at least one of methylene blue, methyl orange, rhodamine B, 2,4-diphenol and tetracycline.

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