CN110124696A - A kind of preparation method of cadmium sulfide and cobalt disulfide heterojunction photocatalyst - Google Patents

Abstract

The invention discloses a method for preparing a heterojunction photocatalyst of cadmium sulfide and cobalt disulfide. The method comprises: hydrothermally reacting sulfur powder and cadmium acetate to form cadmium sulfide, then adding it into a cobalt chloride solution, and then adding sulfur Sodium sulfide, hydrothermal reaction again to obtain cobalt disulfide and cadmium sulfide heterojunction photocatalyst. According to the preparation method of the present invention, there are few types of raw materials, ^cheap and easy to obtain, simple ^process , and environmental protection. Has good stability.

Description

A kind of preparation method of cadmium sulfide and cobalt disulfide heterojunction photocatalyst

technical field

The invention belongs to the technical field of nanometer metal materials and photocatalytic materials, and in particular relates to a preparation method of a heterojunction photocatalyst of cadmium sulfide and cobalt disulfide.

Background technique

Energy is the material basis for human survival and development. At present, the world's energy supply is mainly non-renewable resources such as oil, coal, and natural gas. In order to ensure the energy supply for human development, seeking sustainable new energy sources is an important topic for current and future generations. Semiconductors have been found to enable the photoelectrocatalytic decomposition of water, which is considered to be a promising technology for deep purification of environmental pollution.

The theoretical basis of semiconductor photocatalytic oxidation technology is solid energy band theory, which involves disciplines such as semiconductor science, physical chemistry, material science, surface science and optical science. Transition metal sulfides, such as cadmium sulfide (CdS), molybdenum sulfide (MoS ₂ ), and tungsten sulfide (WS ₂ ), have received extensive attention from researchers in the past 20 years and have achieved rapid development. Among them, cadmium sulfide, which has been studied more, is a kind of semiconductor material with a forbidden band width of about 2.42eV and a maximum absorption peak of light at 514nm, so its electrons in the valence band can be absorbed by visible light and ultraviolet light with a wavelength lower than 514nm. Photoexcited transition to the conduction band, in view of this feature, CdS can be used as a catalyst for natural light (sunlight) catalyzed reactions.

Although compared with semiconductor materials such as TiO ₂ , CdS can directly respond to visible light without wasting energy, but CdS materials are extremely prone to photocorrosion, which severely limits the number of photocatalytic cycles. Therefore, in order to solve this fundamental problem, researchers have proposed many measures to improve the utilization rate of CdS. The most common way is to prepare CdS composite materials by combining different materials or ion doping. The composite materials can also improve the long-wavelength The absorption utilization rate of light realizes the full absorption and utilization of natural light in the visible band region. Noble metal-free cobalt sulfide (CoS ₂ ) has been extensively studied as a substitute for the rare and precious metal platinum in the preparation of photocatalysts. _The CoS2 nanosheets facilitated electron-hole separation, provided catalytically active sites, and inhibited the aggregation of CdS nanomaterials as light absorbers, thereby enhancing the photocatalytic performance.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention aims to provide a method for preparing a heterojunction photocatalyst of cadmium sulfide and cobalt disulfide. The heterojunction photocatalyst, described preparation method comprises the following steps:

Step 1) Disperse sulfur powder and cadmium acetate in ethylenediamine solution, move to a stainless steel autoclave with polytetrafluoroethylene lining, and heat at 200°C for 12 hours;

Step 2) Take the product obtained in step 1) out of the reaction kettle, wash the obtained precipitate several times with deionized water and absolute ethanol, place it in a drying oven at a temperature of 60° C., and then grind it to obtain Pale yellow cadmium sulfide nanomaterials;

Step 3) adding a certain amount of solid cobalt chloride particles into water, stirring to form a solution;

Step 4) Grinding the yellow powder obtained in step 2) and adding it to the cobalt chloride solution obtained in step 3), stirring magnetically, the mass ratio of powder to cobalt chloride is 15:1;

Step 5) Add sodium thiosulfate solid to the mixture obtained in step 4), stir vigorously, and the mass ratio of the amount of sodium hexasulfate added to cobalt chloride in the above step 3) is 6:5;

Step 6) Move the mixture obtained in step 5) to a stainless steel autoclave, and react at 150° C. for 12 hours;

Step 7) Take the product obtained in step 6) out of the reaction kettle, wash the obtained precipitate several times with deionized water and absolute ethanol, place it in a drying oven at a temperature of 60° C., and then grind it to obtain The target product is cobalt disulfide and cadmium sulfide heterojunction photocatalyst.

The mass ratio of sulfur powder and cadmium acetate described in described step 1) is to be dispersed in ethylenediamine and will stir 0.5h, ultrasonic 0.5h makes it form uniform dispersion liquid, and the mass ratio of sulfur powder and cadmium acetate is 1:5, Ethylenediamine is used as a morphology regulator, and the mass ratio of ethylenediamine to sulfur powder is 100:1, which cannot be replaced by other solvents.

The temperature of the stirring reaction in the step 5) is 20° C., and the stirring speed is 700 r/min.

Beneficial effect

According to the preparation method of the cadmium sulfide and cobalt disulfide heterojunction photocatalyst of the present invention, the method has the advantages of few types of raw materials, cheap and easy to obtain, simple process, environmental protection, etc., and the obtained heterojunction photocatalyst has high photocatalytic activity, The optimum hydrogen production can reach 5.54mmol g ^-1 h ^-1 , and it has good stability. The catalyst speeds up the separation of electron-hole pairs by changing the different ratios of CoS ₂ /CdS, improves the utilization rate of visible light, and thus greatly improves the hydrogen production effect.

Description of drawings

Fig. 1 is the CdS/CoS obtained in embodiment 1 and comparative example 1 and ₂ Heterojunction photocatalytic material and CdS, CoS _The X-ray diffraction spectrum of monomer;

Fig. 2 is CdS/CoS prepared in embodiment 1 and comparative example 1 and ₂ Heterojunction photocatalytic material and CdS, CoS _The ultraviolet-visible diffuse reflectance spectrum of monomer;

Fig. 3 is the transmission electron micrograph of the CdS/CoS2 heterojunction photocatalytic material that embodiment ₁ makes;

Fig. 4 is the CdS/CoS that embodiment 1 makes ₂ Heterojunction photocatalytic material surface photovoltaic test contrast chart;

Fig. 5 is a comparison diagram of the hydrogen production effect of the CdS/CoS ₂ heterojunction photocatalytic material prepared in Example 1.

Detailed ways

Hereinafter, the present invention will be described in detail. Before proceeding with the description, it should be understood that the terms used in this specification and appended claims should not be construed as limited to ordinary and dictionary meanings, but should be best interpreted while allowing the inventor to properly define the terms On the basis of the principles of the present invention, explanations are made based on meanings and concepts corresponding to the technical aspects of the present invention. Accordingly, the descriptions set forth herein are preferred examples for illustrative purposes only and are not intended to limit the scope of the invention, so that it should be understood that other, etc. price or improvement.

The following examples are only listed as examples of embodiments of the present invention, and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope of not departing from the essence and design of the present invention all fall into the protection of the present invention. scope. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

Example ₁ : Preparation of CdS/CoS heterojunction photocatalyst

1) Dissolve 0.16g of sulfur powder and 0.8g of cadmium acetate in 9mL of ethylenediamine, stir for 15min, then transfer to a stainless steel autoclave lined with polytetrafluoroethylene, and heat at 200°C for 12h;

2) After the product obtained in step 1) is cooled, washed with water and ethanol several times, dried in a drying oven at 60° C., and then ground to obtain powdered cadmium sulfide;

3) Dissolve 0.02g of cobalt chloride solid particles in 60ml of water and stir for 120min;

4) Add 0.3 g of the powder obtained in step 2) to the solution obtained in step 3), and stir magnetically for 30 minutes;

5) Add 0.024 g of sodium thiosulfate solid to the mixture obtained in step 4), and stir vigorously for 30 min;

6) Move the mixture obtained in step 5) to a stainless steel autoclave, and react at 150° C. for 12 hours;

7) The product obtained in step 6 is taken out from the reaction kettle, washed with water and sewage ethanol for 3 times, placed in a drying oven at 60° C. for 12 hours, and then ground to obtain the target product of cadmium sulfide and cobalt disulfide. Mass catalyst (CdS/CoS ₂ ).

Comparative example 1: the preparation of CdS monomer

Dissolve 0.16g of sulfur powder and 0.8g of cadmium acetate in 9mL of ethylenediamine, stir for 15 minutes, then transfer to a stainless steel autoclave with a polytetrafluoroethylene liner, heat it in water at 200°C for 12 hours, cool the reaction product, and wash it with water Wash with ethanol for 3 times, dry in a drying oven at 60°C, and then grind to obtain powdered cadmium sulfide monomer.

Comparative Example 2: Preparation of CoS ₂ monomer

Dissolve 0.59g of solid cobalt chloride particles and 0.024g of solid sodium thiosulfate in 60ml of water, stir for 120min, then move the solution to a stainless steel autoclave, react at 150°C for 12h, and wash the reaction product with water and ethanol after cooling 3 times, and dried in a drying oven at 60°C, and then ground to obtain powdered cobalt disulfide monomer.

Fig. 1 is the X-ray diffraction spectrum of the CdS/CoS2 heterojunction photocatalyst CdS and CoS2 monomers prepared in Example ₁ and Comparative Examples 1 and ₂ . It can be seen from Figure 1a that all the diffraction peaks of CdS obtained in Comparative Example 1 can be attributed to hexagonal phase CdS (JCPDS 41-1049). Meanwhile, Figure 1b shows that the main diffraction peaks of CoS2 obtained in Comparative Example ₂ correspond one-to-one with the standard tetragonal phase CoS2 (JCPDS _65-3322 ). In Figure 1c, the characteristic peaks of the CdS/CoS2 heterojunction photocatalyst obtained in Example ₁ mainly show the characteristic peaks of CdS monomer, and no obvious characteristic peaks of _CoS2 are found, mainly because of the loading of _CoS2 due to low volume.

Fig. 2 is the ultraviolet-visible absorption spectrum of the CdS/CoS ₂ heterojunction photocatalyst CdS and CoS ₂ monomers prepared in Example 1 and Comparative Examples 1 and 2. As can be seen from the figure, the CoS monomer obtained in Comparative Example ₂ shows a good absorption capacity for visible light, and its forbidden band width is 0.88eV after calculation; the CdS monomer obtained in Comparative Example 1 has a certain visible light Absorption capacity, its absorption edge is 529nm, and its forbidden band width is 2.40eV; when CdS and CoS ₂ form a heterojunction, its visible light absorption edge shows a certain red shift phenomenon, and its absorption edge is 541nm. Therefore, the light absorption ability of the CdS/CoS2 heterojunction photocatalyst obtained in Example ₁ has been greatly improved compared with that of CdS monomer.

3 is a transmission electron micrograph of the CdS/CoS2 heterojunction photocatalyst prepared in Example ₁ . From the results of transmission electron microscopy, it can be seen that a tightly bonded interface is formed between CdS and CoS ₂ in the CdS/CoS ₂ composite, forming a heterojunction structure, which will facilitate the electron transport between the two phases and can effectively inhibit The recombination of photogenerated electron-hole pairs leads to efficient photocatalytic activity.

Fig. 4 is the CdS/CoS2 heterojunction photocatalyst, CdS and CoS2 monomer that make in embodiment ₁ and comparative example 1 and ₂ steady-state photovoltaic test figure, test provides monochrome by a 500W xenon lamp Light. It can be seen that the monomeric CdS prepared in Comparative Example 12 showed an obvious surface photovoltaic response in the range of _300-550nm , but the CoS2 prepared in Comparative Example ₂ had almost no response, indicating that CoS2 in its No photogenerated electron-hole separation occurs in the bandgap range. For the CdS/CoS2 heterojunction photocatalyst prepared in Example ₁ , it can be seen that the photovoltaic signal has been significantly enhanced, and the photovoltaic curve of the composite is not a simple superposition of CdS and _CoS2 monomer signals . Therefore, the formation of CdS/ _CoS2 heterojunction is beneficial to the separation and transfer of photogenerated charges.

Fig. 5 is a comparison chart of the photocatalytic hydrogen production effect of CdS and CoS ₂ monomers of CdS/CoS ₂ heterojunction photocatalysts prepared in Example 1 and Comparative Examples 1 and 2. The specific experimental operation steps of the photocatalytic hydrogen production are as follows: a xenon lamp with an AM1.5G filter is used as a simulated sunlight light source, the intensity of the light source is equivalent to the energy of one sun, and the irradiated area is 17.8cm ² . During the test, the CdS/CoS2 heterojunction photocatalyst, CdS and CoS2 monomers prepared in 0.1g embodiment ₁ and comparative examples 1 and ₂ were dispersed into the aqueous solution of 100mL ascorbic acid, and the concentration of ascorbic acid was 0.75mol/L. Subsequently, the reaction system was evacuated to a vacuum by a vacuum pump, and 1 mL of gas was extracted by sampling every 30 minutes, and the amount of hydrogen produced was analyzed by a gas chromatograph.

It can be seen from Figure 5 that the hydrogen production rates of CdS and CoS ₂ monomers obtained in Comparative Examples 1 and 2 are 1.02 mmol h ^-1 g ^-1 and 0.1 mmol h ^-1 g ^-1 , respectively. However, the hydrogen production rate of the CdS/CoS ₂ heterojunction catalyst obtained in Example 1 has been significantly enhanced to 5.54 mmol h ^-1 g ^-1 , which is 5.4 times and 55.2 times that of CdS and CoS ₂ monomers, respectively. . And after three cycles, the activity of the catalyst did not decrease significantly.

The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the invention without departing from the scope and spirit of the invention. If these changes and modifications are within the scope of the claims of the present invention and equivalent technologies, the intent of the present invention is to include these changes and modifications.

Claims (3)

1. a preparation method of cadmium sulfide and cobalt disulfide heterojunction photocatalyst, said preparation method may further comprise the steps: Step 1) Disperse sulfur powder and cadmium acetate in ethylenediamine solution, move to a stainless steel autoclave with polytetrafluoroethylene lining, and heat at 200°C for 12 hours; Step 2) Take the product obtained in step 1) out of the reaction kettle, wash the obtained precipitate several times with deionized water and absolute ethanol, place it in a drying oven at a temperature of 60° C., and then grind it to obtain Pale yellow cadmium sulfide nanomaterials; Step 3) adding a certain amount of solid cobalt chloride particles into water, stirring to form a solution; Step 4) Grinding the yellow powder obtained in step 2) and adding it to the cobalt chloride solution obtained in step 3), stirring magnetically, the mass ratio of powder to cobalt chloride is 15:1; Step 5) adding sodium thiosulfate solid to the mixture obtained in step 4), stirring vigorously, the mass ratio of the amount of sodium hexasulfate added to cobalt chloride in the above step 3) is 6:5; Step 6) Move the mixture obtained in step 5) to a stainless steel autoclave, and react at 150° C. for 12 hours; Step 7) Take the product obtained in step 6) out of the reaction kettle, wash the obtained precipitate several times with deionized water and absolute ethanol, place it in a drying oven at a temperature of 60° C., and then grind it to obtain The target product is cobalt disulfide and cadmium sulfide heterojunction photocatalyst. 2. preparation method according to claim 1, it is characterized in that, described in step 1) sulfur powder and cadmium acetate are dispersed in ethylenediamine and will stir 0.5h, ultrasonic 0.5h makes it form uniform dispersion, sulfur powder and The mass ratio of cadmium acetate is 1:5. 3. The preparation method according to claim 1, characterized in that, the temperature of the stirring reaction in step 5) is 20° C., and the stirring speed is 700 r/min.