A tannic acid@sulfur vacancy cadmium sulfide composite material and its preparation method and application

Abstract

The present invention relates to the technical field of photocatalytic materials, and in particular to a tannic acid@sulfur vacancy cadmium sulfide composite material, a preparation method thereof, and an application thereof. The preparation method provided by the present invention comprises the steps of: S1. preparing a base catalyst; and S2. coating the base catalyst with tannic acid. The method comprises the steps of introducing sulfur vacancies into cadmium sulfide and coating the surface of the sulfur-vacancy cadmium sulfide with tannic acid, wherein the tannic acid is only loaded on the surface of the cadmium sulfide base catalyst as a co-catalyst without changing the crystal structure of the catalyst itself. By introducing sulfur vacancies into the cadmium sulfide, the utilization rate of light is increased, thereby improving the activity of the catalyst. At the same time, by coating with tannic acid, the recombination of photogenerated carriers is suppressed, thereby improving the separation efficiency of surface photogenerated electron-hole pairs, and thus having better catalytic activity, which can better meet the needs of photocatalytic applications and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic materials, and in particular to a tannic acid@sulfur-vacancy cadmium sulfide composite material, a preparation method thereof, and applications thereof. Background Art

[0002] As a liquid raw material, H2O2 is widely used in water purification, antimicrobial agents, pulp bleaching agents, fuel cells, and other fields. Currently, the main method for producing H2O2 is the anthraquinone route, which suffers from drawbacks such as high energy consumption and the production of toxic byproducts. In comparison, photocatalytic technology offers a more attractive route and method for synthesizing H2O2, potentially being more affordable and environmentally friendly.

[0003] Cadmium sulfide (CdS), an inexpensive semiconductor material, shows promising application prospects in the photocatalytic synthesis of H₂O₂. However, its low photocatalytic efficiency severely restricts its practical application. While its catalytic efficiency can be improved to some extent through semiconductor composites, hierarchical structures, and the introduction of heteroatoms, the effectiveness of a single strategy alone is often insufficient.

[0004] In view of this, the present application aims to provide a tannic acid@sulfur vacancy cadmium sulfide composite material and its preparation method and application, by introducing sulfur vacancies (Sv-CdS) into cadmium sulfide and coating tannic acid (TA) on the surface of sulfur vacancy cadmium sulfide to greatly improve the efficiency of cadmium sulfide photocatalytic production of H2O2. Summary of the Invention

[0005] To solve the above problems, the present invention provides a tannic acid@sulfur vacancy cadmium sulfide composite material, its preparation method and application. By introducing sulfur vacancies (Sv-CdS) into cadmium sulfide and coating tannic acid (TA) on the surface of sulfur vacancy cadmium sulfide, the efficiency of photocatalytic H2O2 production of cadmium sulfide is greatly improved, which can better meet application requirements.

[0006] The technical solution adopted in the present invention is:

[0007] A method for preparing a tannic acid@sulfur-vacancy cadmium sulfide composite material comprises the following preparation steps:

[0008] S1. Preparation of substrate catalyst

[0009] Cadmium acetate dihydrate and thioacetamide are dissolved in propylene diamine and stirred at room temperature until uniformly mixed. The mixture is then placed in an autoclave and reacted at a constant temperature of 190-210°C for 22-26 hours. The mixture is then separated by centrifugation and washed with deionized water and ethanol multiple times, filtered, and dried to obtain a yellow powder base catalyst.

[0010] S2. Tannic acid coated substrate catalyst

[0011] Tannic acid, di(2-hydroxyethyl)iminotris(hydroxymethyl)methane, sodium chloride, base catalyst and ultrapure water were poured into a reaction vessel in sequence, stirred at room temperature for 22-26 hours, and finally washed with an equal amount of deionized water, filtered and dried to obtain a brown powder catalyst.

[0012] A further improvement to the above technical solution is that in step S1, the molar ratio of cadmium acetate dihydrate to thioacetamide is 0.7-0.9:1.

[0013] A further improvement to the above technical solution is that in step S1, the ratio of cadmium acetate dihydrate to propylene diamine is 0.3-0.5:1 mol / L.

[0014] A further improvement to the above technical solution is that in step S1, cadmium acetate dihydrate and thioacetamide are dissolved in propylene diamine and stirred at room temperature for 25-35 minutes until the mixture is uniform.

[0015] A further improvement to the above technical solution is that, in step S1, the mixture is placed in a stainless steel autoclave for constant temperature reaction.

[0016] A further improvement to the above technical solution is that in step S2, the mass ratio of tannic acid, di(2-hydroxyethyl)iminotris(hydroxymethyl)methane, sodium chloride and base catalyst is 0.01-1.5:1:1.5-2:0.1-0.3.

[0017] A further improvement to the above technical solution is that in step S2, the ratio of tannic acid to ultrapure water is 0.01-1.5:50 g / mL.

[0018] A further improvement to the above technical solution is that, in step S2, the opening of the reaction container is wrapped with a layer of plastic wrap.

[0019] Based on the same inventive concept, the present application also provides a tannic acid@sulfur-vacancy cadmium sulfide composite material prepared using the above-mentioned preparation method.

[0020] Based on the same inventive concept, the present application also provides an application of the above-mentioned tannic acid@sulfur-vacancy cadmium sulfide composite material in the photocatalytic synthesis of H2O2.

[0021] The beneficial effects of the present invention are as follows:

[0022] The preparation method provided in the present application introduces sulfur vacancies into cadmium sulfide and coats tannic acid on the surface of the cadmium sulfide with sulfur vacancies. The tannic acid is only loaded on the surface of the cadmium sulfide base catalyst and exists as a co-catalyst without changing the crystal structure of the catalyst itself. By introducing sulfur vacancies into the cadmium sulfide, the utilization rate of light is improved, and the activity of the catalyst is also improved. At the same time, by coating with tannic acid, the recombination of photogenerated carriers is suppressed, thereby making the separation efficiency of photogenerated electron-hole pairs at the surface higher, and making it have higher catalytic activity, which can better meet the needs of photocatalytic applications and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The EPR spectra of the catalytic materials in the examples and comparative examples of the present invention are as follows;

[0024] Figure 2 The XRD patterns of the catalytic materials in the embodiments and comparative examples of the present invention are as follows;

[0025] Figure 3 The UV-visible absorption spectra of the catalytic materials in the embodiments and comparative examples of the present invention are shown in FIG.

[0026] Figure 4 PL spectra of the catalytic materials in the examples and comparative examples of the present invention;

[0027] Figure 5 This is a test chart of the photocatalytic H2O2 production performance of the catalytic materials in the examples and comparative examples of the present invention. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, the present invention will be described more fully below through examples, with preferred embodiments of the present invention provided below. However, the present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. Any other embodiments obtained by modifying or equivalently replacing the technical solution of the present invention without inventive results are within the scope of protection of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0030] The numerical values ​​disclosed in the embodiments of the present invention are approximate values, not definite values. Where errors or experimental conditions permit, all values ​​within the error range may be included without being limited to the specific numerical values ​​disclosed in the embodiments of the present invention.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0032] Example 1

[0033] S1. Preparation of base catalyst (with sulfur vacancies)

[0034] 20 mmol (5.3306 g) of cadmium acetate dihydrate and 25 mmol (1.8783 g) of thioacetamide were weighed and dissolved in 60 mL of propylene diamine at room temperature. The mixture was stirred at room temperature for 30 min until uniformly mixed. The mixture was placed in a stainless steel autoclave with an inner lining volume of 100 mL and reacted at a constant temperature of 200° C. for 24 h. After the reaction, the catalyst was separated by centrifugation and washed with deionized water and ethanol several times, filtered, and dried to obtain a yellow powder base catalyst, which is described as b below.

[0035] S2. Tannic acid coated substrate catalyst

[0036] At room temperature, 0.01 g of tannic acid, 1 g of di(2-hydroxyethyl)iminotris(hydroxymethyl)methane, 1.75 g of sodium chloride, and 0.2 g of base catalyst were weighed, and 50 mL of ultrapure water were measured and poured into a 100 mL beaker in sequence. A rotor was added and the mouth of the beaker was wrapped with a layer of plastic wrap. An electric stirrer was used to stir at room temperature for 24 hours. Finally, the catalyst sample was washed with an equal amount of deionized water, filtered, and dried to obtain a brown powder catalyst, which will be described later as c.

[0037] Example 2

[0038] The difference between this embodiment and embodiment 1 is that in step S2, the amount of tannic acid added is 0.05 g, and the rest is the same as in embodiment 1. The tannic acid@sulfur-vacancy cadmium sulfide composite material prepared in this embodiment is described as d below.

[0039] Example 3

[0040] The difference between this embodiment and embodiment 1 is that in step S2, the amount of tannic acid added is 0.09 g, and the rest is the same as in embodiment 1. The tannic acid@sulfur-vacancy cadmium sulfide composite material prepared in this embodiment is described below as e.

[0041] Example 4

[0042] The difference between this embodiment and embodiment 1 is that in step S2, the amount of tannic acid added is 1.4 g, and the rest is the same as in embodiment 1. The tannic acid@sulfur-vacancy cadmium sulfide composite material prepared in this embodiment is described below as f.

[0043] Comparative Example 1 (no sulfur vacancy)

[0044] At room temperature, 20 mmol (5.3306 g) of cadmium acetate dihydrate and 20 mmol (1.5026 g) of thioacetamide were dissolved in 60 mL of water and stirred at room temperature for 30 min until uniformly mixed. The mixture was placed in a stainless steel autoclave with an inner lining volume of 100 mL and reacted at a constant temperature of 200° C. for 24 h. After the reaction, the catalyst was separated by centrifugation and washed with deionized water and ethanol, filtered, and dried to obtain an orange powder base catalyst, which is described below as a.

[0045] Comparative Example 2

[0046] This comparative example is tannic acid, which is described in g below.

[0047] See also Figure 1 As shown, it is the EPR spectrum of the catalytic materials in the above-mentioned embodiments and comparative examples. It can be seen from the figure that compared with sample a, sample b has obvious g value signals (g=2.064 and g=2.024), indicating that there are sulfur vacancies in the structure of sample b, that is, cadmium sulfide containing sulfur vacancies.

[0048] See also Figure 2 As shown in the figure, it is the XRD spectrum of the catalytic materials in the above-mentioned embodiments and comparative examples. It can be seen from the figure that the diffraction peaks of samples a~f at 23.7°, 26.5°, 28.1°, 43.7°, 47.8° and 51.8° correspond to hexagonal cadmium sulfide, which are respectively attributed to the (100), (002), (101), (110), (103) and (112) crystal planes, and an impurity phase appears at the 36.6° diffraction peak, and the corresponding crystal plane is (102).

[0049] For sample a, the diffraction peak intensity is the highest when the crystal plane is (002), indicating that the sample has good growth on the (002) crystal plane. Conversely, for samples b-f, the diffraction peak intensity is the highest when the crystal plane is (101), indicating that the samples have good growth on the (101) crystal plane. Overall, for samples a and b, regardless of whether there is a sulfur vacancy, the basic structure of the crystal remains unchanged, that is, the basic structure of cadmium sulfide is still retained. For samples b-f, it can be seen that regardless of the amount of tannic acid coated, the crystal structure of the catalyst itself does not change, and the crystal structure is almost the same as that of the catalyst without tannic acid coating. That is, the tannic acid is only loaded on the surface of the cadmium sulfide base catalyst, existing in the form of a co-catalyst, without changing its own crystal structure.

[0050] See also Figure 3 As shown, the catalytic materials a to g in the embodiments and comparative examples of the present application were tested using an ultraviolet-visible spectrophotometer. It can be seen from the test diagram that, except for sample g, the other samples a to f all exhibit typical semiconductor absorption spectra.

[0051] For the sulfur-free sample a, its absorption edge is 597nm. However, the absorption curves of the modified samples b to f show a composite phenomenon in the spectrum, and their absorption edges are smaller than that of sample a, at 529nm. The band gaps calculated according to the Kubelka–Munk equation are 2.08eV for sample a and 2.34eV for samples b to f. See Table 1 below for details:

[0052] Table 1 Absorption edge and band gap width of samples a~f

[0053] sample Absorption edge (nm) Bandgap width (eV) a 597 2.08 b~f 529 2.34

[0054] It can be seen that the band gap corresponding to sample a is relatively smaller than that of samples b~f, which can improve the reduction ability of the photocatalyst to a certain extent, thereby enhancing the catalytic material's absorption of visible light. However, based on the experimental results, the effect of catalysts b~f in producing hydrogen peroxide is significantly better than that of the unmodified catalyst a. It can be seen that although the modified catalyst's ability to absorb visible light has decreased, its utilization rate of light has increased accordingly, and the catalyst's activity is also better.

[0055] In addition to light absorption, the transfer and separation process of photoexcited charges is crucial to the photocatalytic reaction. Therefore, the recombination rate and lifetime of photoexcited carriers are characterized by room temperature PL emission spectroscopy.

[0056] Characterization results such as Figure 4 The following table shows the PL spectra of samples a–f at room temperature under 355 nm excitation. Compared to samples b–f, the photoluminescence intensity of the modified sulfur-vacancy substrate catalysts significantly decreases when coated with varying amounts of tannic acid, indicating that the recombination of photogenerated carriers is suppressed, resulting in a more efficient separation of photogenerated electron-hole pairs and a lower recombination rate on the surface.

[0057] In order to further verify the catalytic effect, the catalytic materials in the above examples and comparative examples were tested for H2O2 production performance. The test results are as follows: Figure 5 As shown in the figure, when the catalyst a without sulfur vacancy is irradiated under visible light, the average H2O2 content produced per hour is relatively low, only 6192μg L -1 For the modified catalysts b to f, under the same conditions, the average H2O2 content produced per hour was 7163 μg L -1 、23156μg L -1 、24306μg L -1 、13793μg L -1 and 13125 μg L -1When only tannic acid was used as the catalyst, the average H2O2 content per hour was 5142 μg L -1 , and the activity is comparable to that of the base catalyst without sulfur vacancies.

[0058] It can be seen that the H2O2 content of the modified catalyst increased by 1.16, 3.74, 3.93, 2.23 and 2.12 times, and the activity of the modified catalyst was improved to a certain extent. When the content of coated tannic acid was 0.05g, the photocatalytic H2O2 production effect was the best and the activity was the highest.

[0059] In summary, the preparation method provided by the present application introduces sulfur vacancies into cadmium sulfide and coats tannic acid on the surface, wherein the tannic acid is only loaded on the surface of the cadmium sulfide base catalyst and exists in the form of a co-catalyst without changing the crystal structure of the catalyst itself; by introducing sulfur vacancies into cadmium sulfide, the utilization rate of light is improved, thereby improving the activity of the catalyst; at the same time, by coating with tannic acid, the recombination of photogenerated carriers is suppressed, thereby increasing the separation efficiency of photogenerated electron-hole pairs at the surface, making it have higher catalytic activity, which can better meet the needs of photocatalytic applications and has good application prospects.

[0060] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a tannic acid@sulfur-vacancy cadmium sulfide composite material, characterized in that: The method comprises the following preparation steps: S1. Preparation of substrate catalyst Cadmium acetate dihydrate and thioacetamide are dissolved in propylene diamine and stirred at room temperature until uniformly mixed. The mixture is then placed in an autoclave and reacted at a constant temperature of 190-210°C for 22-26 hours. The mixture is then separated by centrifugation and washed with deionized water and ethanol multiple times, filtered, and dried to obtain a yellow powder base catalyst. S2. Tannic acid coated substrate catalyst Tannic acid, di(2-hydroxyethyl)iminotris(hydroxymethyl)methane, sodium chloride, base catalyst and ultrapure water were poured into a reaction vessel in sequence, stirred at room temperature for 22-26 hours, and finally washed with an equal amount of deionized water, filtered and dried to obtain a brown powder catalyst.

2. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 1, wherein: In step S1, the molar ratio of cadmium acetate dihydrate to thioacetamide is 0.7-0.9:

1.

3. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 2, wherein: In step S1, the ratio of cadmium acetate dihydrate to propylene diamine is 0.3-0.5:1 mol / L.

4. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 1, wherein: In step S1, cadmium acetate dihydrate and thioacetamide are dissolved in propylene diamine and stirred at room temperature for 25-35 minutes until the mixture is uniform.

5. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 1, wherein: In step S1, the mixture is placed in a stainless steel autoclave for constant temperature reaction.

6. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 1, characterized in that: In step S2, the mass ratio of tannic acid, di(2-hydroxyethyl)iminotris(hydroxymethyl)methane, sodium chloride and base catalyst is 0.01-1.5:1:1.5-2:0.1-0.

3.

7. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 6, wherein: In step S2, the ratio of tannic acid to ultrapure water is 0.01-1.5:50 g / mL.

8. The method for preparing the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 1, wherein: In step S2, the opening of the reaction container is wrapped with a layer of plastic wrap.

9. A tannic acid@sulfur-vacancy cadmium sulfide composite material prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the tannic acid@sulfur-vacancy cadmium sulfide composite material according to claim 8 in photocatalytic synthesis of H2O2.

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