阅读说明：本技术 一种光催化用CdS@SnS2复合材料及其制备方法和应用 (CdS @ SnS for photocatalysis2Composite material and preparation method and application thereof ) 是由 吴芳辉 李红 魏先文 程源晟 文国强 查习文 于 2020-12-25 设计创作，主要内容包括：本发明公开了一种光催化用CdS@SnS2复合材料及其制备方法和应用,属于无机材料合成技术领域。本发明的光催化用CdS@SnS-2复合材料,该复合材料为由CdS与SnS-2复合而成的核壳结构,其中CdS作为内核并呈纳米棒状结构,SnS-2包覆于CdS的表面并呈纳米花样薄片结构。其制备方法为：采用溶剂热法制备CdS纳米材料,然后于含有CdS的乙醇中加入SnCl-4·5H-2O和硫代乙酰胺并进一步采用溶剂热法,即制备得到所述复合材料。采用本发明的技术方案能够有效抑制SnS-2纳米材料的载流子复合,提高其光电转换效率,充分发挥出协同作用,改善原有的单一材料在重金属离子Cr(VI)还原成Cr(III)的反应中的光催化效果,提高催化效率,增强稳定性。(The invention discloses a CdS @ SnS2 composite material for photocatalysis and a preparation method and application thereof, belonging to the technical field of inorganic material synthesis. CdS @ SnS for photocatalysis of the invention 2 The composite material is prepared from CdS and SnS 2 Core-shell structure, with CdS as core and SnS in nano-rod structure 2 Coated on the surface of CdS and in the form of nanometer pattern sheet structure. The preparation method comprises the following steps: preparing CdS nano material by adopting a solvothermal method, and then adding SnCl into ethanol containing CdS 4 ·5H 2 O and thioacetamide and further adopting a solvothermal method to prepare the composite material. By adopting the technical scheme of the invention, the invention canEffective inhibition of SnS 2 The carrier recombination of the nano material improves the photoelectric conversion efficiency of the nano material, fully exerts the synergistic effect, improves the photocatalytic effect of the original single material in the reaction of reducing heavy metal ions Cr (VI) into Cr (III), improves the catalytic efficiency and enhances the stability.)

1. CdS @ SnS for photocatalysis₂A composite material characterized by: the composite material is made of CdS and SnS₂Core-shell structure, with CdS as core and SnS in nano-rod structure₂Coated on the surface of CdS and in the form of nanometer pattern sheet structure.

2. The CdS @ SnS photocatalyst according to claim 1₂A composite material characterized by: the diameter of the composite material is 90-110nm, and the length is 0.8-1.2 μm.

3. The CdS @ SnS photocatalyst according to claim 1₂A composite material characterized by: the diameter of CdS is 15-30nm, and SnS₂The CdS crystal structure grows on the surface of CdS in situ, an obvious boundary exists between two components, and light and dark stripes presented by the boundary of the two components form an included angle of 60 degrees.

4. Photocatalytic CdS @ SnS as defined in any one of claims 1-3₂The preparation method of the composite material is characterized by comprising the following steps: nano rod-shaped CdS and SnCl₄·5H₂O and thioacetamide are put into a solvent to be uniformly mixed and put into a high-pressure reaction kettle to react, so that SnS is reacted₂The nano sheet grows in situ on the CdS nano rod to form a binary heterojunction composite material CdS @ SnS with a core-shell structure₂。

5. Photocatalytic CdS @ SnS according to claim 4₂The preparation method of the composite material is characterized in that the preparation process of the nano rod-shaped CdS comprises the following steps: adding CdCl₂·2.5H₂O and CH₄N₂S sequentially adding ethylene glycolAnd (3) in amine, stirring and mixing uniformly, reacting for 36-60 hours in a high-pressure reaction kettle at a constant temperature of 150-170 ℃, and washing and drying after the reaction is finished to obtain the CdS nanorod sample.

6. Photocatalytic CdS @ SnS according to claim 5₂The preparation method of the composite material is characterized by comprising the following steps: the CdCl₂·2.5H₂O and CH₄N₂The mol ratio of S is 1: 2.5-3.5, the drying temperature is 50-80 ℃, and the drying time is 10-15 h.

7. Photocatalytic CdS @ SnS according to any one of claims 4-6₂The preparation method of the composite material is characterized by comprising the following steps: the addition amount of the CdS nanorod is SnCl₄·5H₂0.4-0.9 mass% of O, and the addition amount of the thioacetamide is SnCl₄·5H₂2.5 to 4 times of the molar weight of O.

8. Photocatalytic CdS @ SnS according to claim 7₂The preparation method of the composite material is characterized by comprising the following steps: the reaction temperature is 150-180 ℃, and the reaction time is 10-15 h.

9. Photocatalytic CdS @ SnS according to claim 8₂The preparation method of the composite material is characterized by comprising the following steps: the reaction solvent adopts ethanol, the CdS nanorods are firstly added into the ethanol and are uniformly dispersed by ultrasound, and then SnCl is added into the ethanol₄·5H₂O and thioacetamide are evenly dispersed by ultrasonic.

10. CdS @ SnS prepared according to the method of any one of claims 4-9₂Application of the heterojunction composite material as a photocatalyst in reducing Cr (VI) in an aqueous phase.

Technical Field

The invention belongs to the technical field of inorganic material synthesis, and particularly relates to CdS @ SnS₂A composite material, a simple preparation method thereof and application of the composite material as a catalyst in photoreduction of Cr (VI) in polluted water.

Background

Water is used as the source of life, and is closely related to human health. However, in recent years, environmental water quality is continuously deteriorated due to heavy metal ions discharged from industries such as tanning, metallurgy, paint and textile, wherein Cr (VI) has strong toxicity, and diseases such as cancer, dermatitis, liver damage and ulcer can be induced by drinking the water for a long time, so that the water is widely concerned by researchers. The World Health Organization (WHO) stipulates that the maximum allowable concentration of Cr (VI) in drinking water is 0.05mg/L, so that the method for measuring and treating Cr (VI) in an environmental water sample by adopting an efficient and convenient method has great theoretical and practical significance. At present, the main treatment method of the Cr (VI) containing wastewater is to reduce the Cr (VI) containing wastewater into low-toxicity Cr (III) or chromium hydroxide (Cr (OH)₃) And removing the precipitate. Compared with the traditional Cr (VI) treatment technology, such as adsorption, membrane filtration, chemical precipitation and the like, the method for photocatalytic reduction of Cr (VI) has the advantages of low energy consumption, low cost, high removal efficiency, environmental friendliness and the like, and is considered to be a green and efficient water treatment method.

A central problem in the field of photocatalysis is the choice of catalyst, however, most metal oxides (e.g., TiO)₂，Ta₂O₅And ZrO₂) The band gap of the material is wide, and only ultraviolet rays and near ultraviolet rays can be absorbed, so that the photocatalytic efficiency and the apparent quantum yield are reduced; metal nitrides (e.g. Ta)₃N₅And Ge₃N₄) The synthesis of (A) often requires at high temperatures and at toxic NH₃Is carried out under the condition; in contrast, many metal sulfide semiconductors (e.g., CuInS)₂PbS) has been widely studied in the reduction of cr (vi) due to its narrow band gap and high utilization of visible light, but these materials contain toxic or expensive elements, which are liable to cause secondary environmental pollution. SnS₂The catalyst has the characteristics of rich raw materials, low cost, no toxicity, narrow band gap (2.1 ev), capability of responding to visible light and the like, develops into a Cr (VI) photocatalyst with great research value, but SnS₂The method has the problems of easy recombination of electron hole pairs, poor photocatalytic stability, insufficient solar spectrum absorption, low reactivity and the like, thereby greatly limiting the possibility of practical application.

To further improve SnS₂The Chinese patent application No. 201910306838.6 discloses a method for preparing a layered attached spherical zinc sulfide/tin disulfide core-shell heterojunction photocatalyst with visible light response, and the application uses SnS₂The spherical ZnS/SnS2 core-shell heterojunction photocatalyst has a large specific surface area and a narrow forbidden band width, so that the photoabsorption and catalytic activity of the catalyst can be improved to a certain extent, but a plurality of organic solvents are used in a solvent system, the pollution degree is high, the composite material is actually used for treating pharmaceutical wastewater under visible light, and the good and bad performance of the material is analyzed by calculating the COD removal rate of the wastewater.

Disclosure of Invention

1. Problems to be solved

The invention aims to solve the problem of the prior SnS₂The CdS @ SnS2 composite material for photocatalysis and the preparation method and application thereof are provided for solving the problems of easy recombination, poor stability and low catalytic efficiency in heavy metal ion Cr (VI) reduction catalysis. By adopting the technical scheme of the invention, the SnS can be effectively inhibited₂The carrier recombination of the nano material improves the photoelectric conversion efficiency thereof and fully exerts the synergyThe photocatalysis effect of the original single material in the reaction of reducing heavy metal ions Cr (VI) into Cr (III) is improved, the catalysis efficiency is improved, and the stability is enhanced.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

first, the invention relates to CdS @ SnS for photocatalysis₂The composite material is prepared from CdS and SnS₂Core-shell structure, with CdS as core and SnS in nano-rod structure₂Coated on the surface of CdS and in the form of nanometer pattern sheet structure.

Furthermore, the diameter of the composite material is 90-110nm, and the length of the composite material is 0.8-1.2 μm.

Further, the diameter of CdS is 15-30nm, and SnS₂The CdS crystal structure grows on the surface of CdS in situ, an obvious boundary exists between two components, and light and dark stripes presented by the boundary of the two components form an included angle of 60 degrees.

Secondly, the invention discloses CdS @ SnS for photocatalysis₂The preparation method of the composite material comprises the steps of mixing nano rod-shaped CdS and SnCl₄·5H₂O and thioacetamide are put into a solvent to be uniformly mixed and put into a high-pressure reaction kettle to react, so that SnS is reacted₂The nano sheet grows in situ on the CdS nano rod to form a binary heterojunction composite material CdS @ SnS with a core-shell structure₂。

Furthermore, the preparation process of the nano rod-shaped CdS comprises the following steps: adding CdCl₂·2.5H₂O and CH₄N₂And S is sequentially added into ethylenediamine, uniformly stirred and mixed, and reacts in a high-pressure reaction kettle at a constant temperature of 150-170 ℃ for 36-60 hours, and after the reaction is finished, the CdS nanorod sample is obtained by washing and drying.

Further, the CdCl₂·2.5H₂O and CH₄N₂The mol ratio of S is 1: 2.5-3.5, the drying temperature is 50-80 ℃, and the drying time is 10-15 h.

Furthermore, the addition amount of the CdS nanorod is SnCl₄·5H₂0.4 to 0.9 mass% of O, sulfurThe amount of the acetamide is SnCl₄·5H₂2.5 to 4 times of the molar weight of O.

Furthermore, the reaction temperature is 150-180 ℃, and the reaction time is 10-15 h.

Furthermore, the reaction solvent is ethanol, the CdS nanorods are firstly added into the ethanol and are uniformly dispersed by ultrasound, and then SnCl is added into the ethanol₄·5H₂O and thioacetamide are evenly dispersed by ultrasonic.

Thirdly, the CdS @ SnS prepared by the invention₂Application of the heterojunction composite material as a photocatalyst in reducing Cr (VI) in an aqueous phase.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention relates to CdS @ SnS for photocatalysis₂The composite material is prepared from CdS and SnS₂Core-shell structure formed by compounding CdS and SnS₂So as to effectively improve SnS₂The reactivity and the light energy utilization rate of the compound are overcome, and the SnS is overcome₂The defects of easy recombination of electron hole pairs, poor photocatalytic stability and insufficient solar spectrum absorption exist in the photocatalyst.

(2) The invention relates to CdS @ SnS for photocatalysis₂Composite material, in which CdS is used as core and has a nano-rod-like structure, SnS₂The CdS-coated nano-pattern sheet structure is formed by coating the CdS surface, and an obvious boundary exists between the two components, so that the composite material with the structural form is favorable for further and fully exerting SnS₂The synergistic effect with CdS promotes SnS₂The adsorption to Cr (VI) can quickly reduce Cr (VI) in the polluted water, thereby reducing the environmental pollution.

(3) CdS @ SnS for photocatalysis of the invention₂Preparation method of composite material, nano-rod-shaped CdS and SnCl₄·5H₂O is used as a reaction raw material, and reaction process parameters such as the addition amount of the nano rod-shaped CdS, the reaction temperature and the reaction time are strictly controlled, so that SnCl can be used₄·5H₂O in-situ growth on surface of nano rod-shaped CdSAnd is in a nano pattern sheet structure, thereby greatly increasing the specific surface area of the composite material, improving the active site, and simultaneously reducing the annihilation rate of electron and hole, thus being beneficial to enhancing the photoelectric conversion efficiency₂Adsorbing adjacent Cr (IV), irradiating the surface of the composite nano material by sunlight and SnS on the surface of the core shell₂The active sites are excited to photocatalytically reduce Cr (IV) adsorbed on the surface of the Cr (IV) to degrade the Cr (III) into low-toxicity Cr (III).

(4) CdS @ SnS for photocatalysis of the invention₂The preparation method of the composite material has the advantages of simple preparation process, cheap raw materials, less consumption, low cost, mild reaction conditions and energy conservation and consumption reduction.

(5) The heterojunction material is constructed by compounding CdS which is low in cost and easy to prepare and SnS2 which is nontoxic and narrow in band gap, so that SnS is effectively enhanced₂The dispersibility of the photocatalyst improves the electron transfer characteristic, reduces the charge hole recombination rate and obviously improves the photocatalytic activity. When the composite material is used for photocatalytic reduction of Cr (IV), the degradation rate is obviously higher than that of a single material, the material is optimized, and the composite material is more environment-friendly.

(6) The composite material of the invention has good stability when being used for photocatalytic reduction of Cr (IV), and has good recycling property after being regenerated by dilute hydrochloric acid.

Drawings

FIG. 1 is CdS @ SnS₂Schematic diagram of catalytic reduction of Cr (VI) by the composite material.

FIG. 2 is CdS (300) @ SnS prepared in example 1₂(c) With CdS (a), SnS₂(b) X-ray powder diffraction (XRD) pattern of (a).

FIG. 3 is CdS (300) @ SnS prepared in example 1₂Scanning Electron Micrograph (SEM) (a); CdS (B) and CdS (300) @ SnS₂(C) Transmission Electron Micrograph (TEM) and CdS (300) @ SnS₂High resolution transmission electron microscopy (HR-TEM) (D).

FIG. 4 shows SnS prepared in example 1₂CdS and CdS (300) @ SnS₂The photocatalytic Cr (VI) reduction curve (A) and the quasi-first order reaction kinetic fitting curve (B) of the sample.

FIG. 5 is a graph showing the comparison of the addition amount of CdS and the apparent rate constant of the composite material in photocatalytic reduction of Cr (VI).

FIG. 6 is a graph comparing the effect of CdS addition on the morphology of the composite material structure.

Detailed Description

SnS₂Due to the characteristics of rich raw materials, low cost, no toxicity, narrow band gap (2.1 ev), capability of responding to visible light and the like, the photocatalyst becomes a Cr (VI) photocatalyst with great research value in recent years, but the photocatalyst also has the problems of easy recombination of electron hole pairs, poor photocatalytic stability, lower catalytic reduction efficiency of Cr (VI) and the like, thereby limiting the practical popularization and application of the photocatalyst. Aiming at the current situation, the invention provides a method for preparing CdS @ SnS₂The method for preparing the composite material specifically comprises the following steps (the reaction principle is shown in figure 1):

the first step of reaction is to prepare a CdS nanorod sample, and the specific process is as follows:

respectively weighing a certain amount of CdCl₂·2.5H₂O and CH₄N₂And S, sequentially adding the S into ethylenediamine with a certain volume, stirring to uniformly mix, transferring into a high-pressure reaction kettle, putting into an oven, reacting at a constant temperature of 150-170 ℃ for 36-60 h, centrifuging, washing, and drying in vacuum (drying at 50-80 ℃ for 10-15 h) to obtain the CdS nanorod sample.

The second step of reaction is to prepare CdS @ SnS with a core-shell structure₂The composite material comprises the following specific processes:

weighing a certain amount of CdS nanorods, adding the CdS nanorods into ethanol with a certain volume, ultrasonically dispersing the CdS nanorods uniformly, and sequentially adding a certain amount of SnCl₄·5H₂Continuously and uniformly dispersing O and thioacetamide by ultrasonic waves, transferring the O and thioacetamide into a high-pressure reaction kettle, reacting for 10-15 h at a constant temperature of 150-180 ℃, respectively centrifugally washing the precipitate for 3-4 times by using ultrapure water and absolute ethyl alcohol, placing the precipitate in a vacuum drying oven, drying for 10-15 h at 50-80 ℃, and collecting to obtain the core-shell structure composite material marked as CdS @ SnS₂。

The CdS and SnS which contain sulfur vacancy, have large specific surface area and have visible light absorption capacity and are low in cost and easy to prepare₂The nano material is used as a reaction raw material, and simple two-step solvothermalThe method prepares SnS by taking CdS nano-rods as cores₂Rod-shaped composite material as shell, formed by CdS and SnS₂Thereby effectively inhibiting SnS₂The carrier recombination of the nano material improves the photoelectric conversion efficiency of the nano material, fully exerts the synergistic effect of the nano material and the carrier, improves the photocatalytic effect of the original single material in the reaction of reducing heavy metal ions Cr (VI) into Cr (III), improves the catalytic efficiency and enhances the stability of the catalyst.

Although many researchers have studied composite materials as catalysts in various catalytic fields in recent years, it should be especially noted that the catalytic principles in different fields are different, the requirements for catalysts are different, and different substances are not randomly compounded to achieve better catalytic effects. Meanwhile, for the same application field, the composition, structure and morphology of the composite material all affect the specific catalytic effect, such as the catalytic efficiency of the catalyst and the stability of the catalyst. The differences in the structure and morphology of the obtained product can be caused by different selection of specific preparation processes, types and proportions of reactants, various reaction conditions and the like. The method selects the solvothermal method and strictly controls reaction process parameters, particularly the addition amount of CdS, reaction temperature and reaction time, so that SnS can be controlled₂The CdS grows on the surface of CdS in situ and is uniformly dispersed in a pattern sheet shape, so that the non-toxic and cheap SnS is effectively enhanced₂The dispersibility of the composite material greatly increases the specific surface area of the composite material, improves the active sites, improves the electron transfer characteristics of the composite material, and reduces the charge hole recombination rate, thereby obviously improving the photocatalytic activity. When SnS₂Adsorbing adjacent Cr (IV), irradiating the surface of the composite nano material by sunlight and SnS on the surface of the core shell₂The active sites are excited to photocatalytically reduce Cr (IV) adsorbed on the surface of the Cr (IV) to degrade the Cr (III) into low-toxicity Cr (III).

Specifically, when the reaction temperature is too high or too low, patterned flaky SnS cannot be formed₂The dispersion is not uniform, the addition amount of CdS influences the size, compactness and dispersion uniformity of the shell-core material structure, and when the addition amount of CdS is small, the obtained composite material is obtainedThe diameter of the composite material is large, the coating is uneven and loose, and when the addition amount of CdS is large, SnS can be caused₂The supported amount of (a) is significantly reduced, thereby significantly reducing the photocatalytic performance. The invention can increase the coating range and SnS by optimally controlling the addition of CdS₂The uniformity of load and the compactness and compactness of the structure are ensured, and the effect of photocatalytic reduction of Cr (IV) is ensured, wherein when the addition amount of CdS is SnCl₄·5H₂The best effect is obtained when the mass of O is 0.85.

The present invention will be further described in the following detailed description, which shows the essential features and significant effects of the present invention, but they do not limit the present invention in any way, and those skilled in the art can make modifications and variations which are not essential to the present invention, and fall within the scope of the present invention. Wherein the morphology of the reaction product in the examples was determined using an X-ray powder diffractometer (D8 ADVANCE model, Bruker, Germany), a scanning electron microscope (S-4800, Hitachi, Japan) and a field emission high-resolution transmission electron microscope (HT-7100, Hitachi, Japan); the photocatalysis experiment is completed by adopting a PCX-50C Discover type multi-channel photocatalysis reactor produced by Beijing Pofely science and technology Limited company; the ultraviolet-visible absorption spectrum (UV-Vis) of the product was determined using a Hitachi UV-4100 model ultraviolet-visible absorption spectrometer.

Example 1

4.62g CdCl were weighed out separately₂·2.5H₂O (0.02mol) and 4.62g CH₄N₂And S (0.06mol) is sequentially added into 60mL of ethylenediamine, stirred for 15min to be uniformly mixed, transferred into a high-pressure reaction kettle, put into an oven, reacted for 48h at the constant temperature of 160 ℃, then respectively centrifugally washed for 3 times by using ultrapure water and absolute ethyl alcohol, finally put into a vacuum drying oven, dried for 12h at 70 ℃ and collected to obtain the CdS nanorod sample.

Weighing 300mg CdS nanorods, adding the CdS nanorods into 80mL ethanol, performing ultrasonic treatment for 15min to uniformly disperse the CdS nanorods, and sequentially weighing 350mg SnCl₄·5H₂Adding O (1.24mmol) and 300mg TAA (3.99mmol) into the mixed solution, ultrasonically dispersing for 15min, transferring into a high-pressure reaction kettle, and reacting at constant temperature of 160 deg.C for 12hThen respectively centrifugally washing the precipitate for 4 times by using ultrapure water and absolute ethyl alcohol, drying the precipitate for 12h at 70 ℃ in a vacuum drying oven, and collecting the dried precipitate to obtain the composite material with the core-shell structure, wherein the mark is CdS (300) @ SnS₂。

(1) Performance characterization

CdS and SnS by X-ray powder diffractometer₂And CdS (300) @ SnS prepared in this example₂The results of the phase analysis are shown in FIG. 2. As can be seen from fig. 2a, the CdS prepared in this example has diffraction peaks at 25 °, 26.5 °, 28.2 °, 43.8 °, 47.8 ° and 51.9 ° in the spectrogram, and respectively corresponds to the (100), (002), (101), (110), (103) and (112) crystal planes in the pure phase of hexagonal wurtzite CdS (JCPDS 41-1049); as can be seen from FIG. 2b, SnS prepared in this example₂Diffraction peaks at 15 °, 28.2 °, 32.1 °, 41.9 °, 50 °, 52.5 ° and 55 ° in the spectrum correspond to the hexagonal phase SnS in the standard card, respectively₂The (001), (100), (101), (102), (110), (111) and (103) crystal faces in the pure phase (JCPDS 23-0677) show that the SnS prepared by the present example₂And CdS is a single pure phase. Composite CdS (300) @ SnS prepared in this example₂In the spectrum (fig. 2c), several distinct characteristic peaks are visible, corresponding to SnS, respectively₂The (111), (110), (200) and (004) crystal planes of CdS, and other characteristic peaks correspond to the (100), (002), (101), (102), (110), (220), (112), (201), (203), (210), (114), (105) and (204) crystal planes of CdS, respectively, indicating that the two materials are successfully recombined.

The morphology of the composite material obtained in this example was analyzed by using a Scanning Electron Microscope (SEM) and a Transmission Electron Microscope (TEM), respectively, and the results are shown in fig. 3. From CdS (300) @ SnS₂SEM image (FIG. 3a) of the composite material shows that the sample has a rod shape overall, a diameter of about 100nm and a length of about 1 μm, and CdS is located in the core, and the surface of the CdS is largely flower-shaped₂The sheet is covered. TEM image of CdS (FIG. 3b) shows that CdS nanorods synthesized in ethylenediamine are uniform in size and smooth in surface, with a diameter of about 20 nm. As shown in FIG. 3c, when CdS nanomaterial is used as core, several layers of SnS sheets are grown in situ on the surface₂Later, two different components are presentThe high resolution transmission electron microscope image (FIG. 3d) shows that the bright and dark stripes of the bi-component boundary are about 60 degrees, the lattice spacing is 0.315nm, and the spacing corresponds to the hexagonal phase SnS₂(100) And (010) crystal face, and the light and dark stripes with the lattice spacing of 0.334nm correspond to the CdS (111) crystal face.

The visible light transient photocurrent response test of each sample intuitively reflects the photo-generated current condition of the sample generated under the excitation of visible light, so that the change curve of the current density of various materials along with time is further researched. As a result, the photo-generated current density of the composite material obtained in the embodiment is obviously different from that of a single material, namely CdS (300) @ SnS under the bias voltage of-0.2V₂The photo-generated current density of the composite material is far greater than that of pure CdS or pure SnS₂The value of (b) indicates that the composite material has an optimal response to visible light and can be used as a photocatalyst.

(2) Testing of catalytic Cr (VI) reduction reaction Performance

The target product is used as a catalyst, and the photocatalytic effect of the target product on the reduction reaction of Cr (VI) in an aqueous phase is researched.

Using 100mW cm^-2White LED with irradiation intensity irradiates an aqueous solution containing Cr (VI), the photocatalytic reduction performance of various materials on the Cr (VI) in the water is tested under the condition that other sacrificial agents are not added, and diphenylcarbodihydrazide (DPC; the concentration of DPC is 2g L)^-1) The Cr (VI) content in the aqueous phase was detected and analyzed by color-developing spectrophotometry (GB/T7467-1987), as shown in FIG. 4. As can be seen from the photocatalytic Cr (VI) reduction curve (such as 4A), CdS (300) @ SnS obtained in this example₂The rate of the photocatalytic reduction of Cr (VI) is obviously greater than that of CdS and SnS₂The catalytic processes of these materials conformed to a quasi-first order reaction (FIG. 4B), from which CdS (300) @ SnS was calculated₂Material, CdS material and SnS₂The rate constants corresponding to the materials are respectively 0.272min^-1、0.0341min^-1And 0.00739min^-1I.e. CdS (300) @ SnS₂The reduction efficiency of Cr (VI) in 16min reaches 100 percent, and the rate constants are CdS and SnS₂8 times and 36.8 times. This is mainly due to CdS and SnS₂Separation of composite structure heterojunction to current carrier and to visible lightThe absorption plays a great promoting role, so that the catalytic performance of the composite material is obviously higher than that of pure CdS and pure SnS₂A material.

In this example, the influence of the added amount of CdS nanorods on the composite material structure and photocatalytic activity (the cr (vi) concentration in the system is the same, and the light source and the illumination time are also the same) is further studied, as shown in fig. 5 and 6 (the added amount of CdS is 0, 150, 300, and 450mg from left to right, respectively). As can be seen, increasing the amount of CdS resulted in the production of CdS @ SnS₂The shell-core material has a more compact structure, the coating range is enlarged, the diameter of the generated composite material is reduced, and SnS loaded on the surface of CdS₂More uniform, and is more beneficial to the reaction of photocatalytic reduction of Cr (IV). However, when the amount of CdS exceeds 300mg, the diameter of the composite material is further reduced, but the loaded SnS₂The amount is significantly reduced, resulting in a significant reduction in the post-photocatalytic performance.

In order to deeply evaluate the catalytic activity of the catalyst, CdS (300) @ SnS is adopted₂The composite material is subjected to photocatalytic Cr (VI) reduction cycle experiments (not shown). As a result, the photocatalytic reduction activity of Cr (VI) is attenuated to some extent after four cycles of use. In order to improve the condition, low-concentration hydrochloric acid is selected for reacting CdS (300) @ SnS₂The catalyst is treated and the catalytic performance of the catalyst is retested, and the catalytic activity of the catalyst is found to be effectively recovered and is obviously higher than the rate of the second cycle reaction, so that the catalyst has better regeneration and stability and can be expanded to practical application.

Example 2

4.62g CdCl were weighed out separately₂·2.5H₂O (0.02mol) and 4.24g CH₄N₂And (3) sequentially adding S (0.055mol) into 50mL of ethylenediamine, stirring for 10min to uniformly mix, transferring into a high-pressure reaction kettle, putting into an oven, reacting at a constant temperature of 150 ℃ for 60h, respectively centrifuging and washing the precipitate for 3 times by using ultrapure water and absolute ethyl alcohol, finally putting into a vacuum drying oven, drying at 50 ℃ for 15h, and collecting the CdS nanorod sample.

Weighing 300mg CdS nanorods, adding the CdS nanorods into 70mL ethanol, performing ultrasonic treatment for 10min to uniformly disperse the CdS nanorods, and sequentially weighing 350mg SnCl₄·5H₂Adding O (1.24mmol) and 250mg Thioacetamide (TAA) (3.32mmol) into the mixed solution, ultrasonically dispersing for 10min, transferring into a high-pressure reaction kettle, reacting at a constant temperature of 150 ℃ for 15h, respectively centrifuging and washing the precipitate for 3 times by using ultrapure water and absolute ethyl alcohol, drying in a vacuum drying oven at 50 ℃ for 15h, and collecting to obtain the composite material with the core-shell structure, wherein the mark is CdS (300) @ SnS₂。

Example 3

4.62g CdCl were weighed out separately₂·2.5H₂O (0.02mol) and 4.24g CH₄N₂And (3) sequentially adding S (0.055mol) into 50mL of ethylenediamine, stirring for 10min to uniformly mix, transferring into a high-pressure reaction kettle, putting into an oven, reacting at a constant temperature of 150 ℃ for 60h, respectively centrifuging and washing the precipitate for 4 times by using ultrapure water and absolute ethyl alcohol, finally putting into a vacuum drying oven, drying at 60 ℃ for 13h, and collecting the CdS nanorod sample.

Weighing 300mg CdS nanorods, adding the CdS nanorods into 80mL ethanol, performing ultrasonic treatment for 15min to uniformly disperse the CdS nanorods, and sequentially weighing 350mg SnCl₄·5H₂Adding O (1.24mmol) and 350mg TAA (4.66mmol) into the mixed solution, ultrasonically dispersing for 20min, transferring into a high-pressure reaction kettle, reacting at 180 ℃ for 10h at constant temperature, respectively centrifuging and washing the precipitate for 4 times with ultrapure water and absolute ethyl alcohol, drying in a vacuum drying oven at 60 ℃ for 13h, and collecting to obtain the composite material with the core-shell structure, wherein the label is CdS (300) @ SnS₂。

Example 4

4.62g CdCl were weighed out separately₂·2.5H₂O (0.02mol) and 4.24g CH₄N₂And (3) sequentially adding S (0.055mol) into 50mL of ethylenediamine, stirring for 20min to uniformly mix, transferring into a high-pressure reaction kettle, putting into an oven, reacting at a constant temperature of 170 ℃ for 45h, respectively centrifuging and washing the precipitate for 4 times by using ultrapure water and absolute ethyl alcohol, finally putting into a vacuum drying oven, drying at 50 ℃ for 15h, and collecting the CdS nanorod sample.

Weighing 300mg CdS nanorods, adding the CdS nanorods into 70mL ethanol, performing ultrasonic treatment for 10min to uniformly disperse the CdS nanorods, and sequentially weighing 350mg SnCl₄·5H₂O (1.24mmol) and 250mg TAA (3)32mmol) is added into the mixed solution, after being dispersed evenly by ultrasonic for 12min, the mixed solution is transferred into a high-pressure reaction kettle to react for 12h at the constant temperature of 170 ℃, then the precipitate is respectively centrifugally washed for 4 times by ultrapure water and absolute ethyl alcohol, the precipitate is placed in a vacuum drying oven to be dried for 15h at the temperature of 50 ℃ and then collected, and the composite material with the core-shell structure can be obtained, and the mark is CdS (300) @ SnS₂。

Example 5

4.62g CdCl were weighed out separately₂·2.5H₂O (0.02mol) and 4.62g CH₄N₂And S (0.06mol) is sequentially added into 60mL of ethylenediamine, stirred for 15min to be uniformly mixed, transferred into a high-pressure reaction kettle, put into an oven, reacted at the constant temperature of 150 ℃ for 54h, respectively centrifugally washed for 4 times by using ultrapure water and absolute ethyl alcohol, finally put into a vacuum drying oven, dried for 12h at 70 ℃ and collected to obtain the CdS nanorod sample.

Weighing 150mg CdS nanorods, adding the CdS nanorods into 90mL ethanol, performing ultrasonic treatment for 20min to uniformly disperse the CdS nanorods, and sequentially weighing 350mg SnCl₄·5H₂Adding O (1.24mmol) and 350mg TAA (4.66mmol) into the mixed solution, ultrasonically dispersing for 20min, transferring into a high-pressure reaction kettle, reacting at a constant temperature of 170 ℃ for 10h, respectively centrifuging and washing the precipitate for 4 times by using ultrapure water and absolute ethyl alcohol, drying in a vacuum drying oven at 80 ℃ for 10h, and collecting to obtain the composite material with the core-shell structure, wherein the label is CdS (150) @ SnS₂。

Example 6

4.62g CdCl were weighed out separately₂·2.5H₂O (0.02mol) and 5.01g CH₄N₂And (3) sequentially adding S (0.065mol) into 70mL of ethylenediamine, stirring for 20min to uniformly mix, transferring into a high-pressure reaction kettle, putting into an oven, reacting at a constant temperature of 170 ℃ for 36h, respectively centrifugally washing the precipitate for 3 times by using ultrapure water and absolute ethyl alcohol, finally putting into a vacuum drying oven, drying at 80 ℃ for 10h, and collecting the CdS nanorod sample.

Weighing 200mg CdS nanorods, adding the CdS nanorods into 90mL ethanol, performing ultrasonic treatment for 20min to uniformly disperse the CdS nanorods, and sequentially weighing 350mg SnCl₄·5H₂O (1.24mmol) and 350mg TAA (4.66mmol) are added into the mixed solution, after being dispersed evenly by ultrasonic for 20min,transferring into a high-pressure reaction kettle, reacting at 180 deg.C for 10h, centrifuging and washing the precipitate with ultrapure water and anhydrous ethanol for 3 times, drying at 80 deg.C for 10h in a vacuum drying oven, and collecting to obtain core-shell composite material labeled as CdS (200) @ SnS₂。