A photocatalyst and a method for preparing the same

Abstract

The application discloses a kind of photocatalyst and preparation method thereof, the photocatalyst is flower ball layer structure, composition includes SnS2, SnS, the molar ratio of SnS2 With SnS is 1-2.5:1.The preparation method of the photocatalyst, including the following steps: (1) tin tetrachloride pentahydrate, sulfur source is placed in first liquid, carries out first hydrothermal reaction, obtains SnS2;(2) to SnS2 Adding stannous chloride dihydrate and sulfur source, carries out second hydrothermal reaction, washes, obtains SnS2@SnS photocatalyst and dries.This application provides photocatalyst, can achieve the effect of excellent reduction performance.

Description

Technical Field

[0001] This invention relates to photocatalytic materials, and more particularly to a photocatalyst and its preparation method. Background Technology

[0002] Transition metal sulfides have attracted much attention in the field of photocatalytic reduction due to their tunable band structure. However, single-component sulfides have inherent defects that limit their reduction performance. While cadmium sulfide (CdS) exhibits visible light response due to its narrow bandgap, the accumulation of photogenerated holes in the valence band leads to irreversible auto-oxidation and severe photocorrosion, resulting in catalyst deactivation. Molybdenum disulfide (MoS2) exhibits reduction activity only at its edge sites and has low carrier mobility; the Cr(VI) reduction rate of monolayer MoS2 is less than 30% of that of SnS2. Zinc sulfide (ZnS) has an excessively wide bandgap, responding only to ultraviolet light, with a solar light utilization rate of <5%. Its reduction kinetic constant is 1-2 orders of magnitude lower than that of narrow-bandgap sulfides. Therefore, existing technologies suffer from insufficient catalyst reducibility. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a photocatalyst with excellent reduction performance; another purpose of this invention is to provide a method for preparing the above-mentioned photocatalyst.

[0004] Technical solution: The photocatalyst of the present invention is characterized in that the photocatalyst has a flower-shaped layered structure, and the components include SnS2 and SnS, wherein the molar ratio of SnS2 to SnS is 1-2.5:1.

[0005] The method for preparing the photocatalyst of the present invention includes the following steps: (1) Tin tetrachloride pentahydrate and sulfur source were placed in a liquid and subjected to a first hydrothermal reaction to obtain SnS2; (2) Add stannous chloride dihydrate and sulfur source to SnS2 for a second hydrothermal reaction, then clean and dry to obtain SnS2@SnS photocatalyst.

[0006] In step (1), the molar ratio of tin tetrachloride pentahydrate to sulfur source is 1:3-6.

[0007] The sulfur source is thioacetamide or thiourea.

[0008] The liquid is alcohol or deionized water.

[0009] After the raw materials mentioned in step (1) are mixed, they are added to the pretreated carbon paper. The pretreatment process of the carbon paper is as follows: the carbon paper is cleaned and dried, and then subjected to carbon fiber plasma surface treatment.

[0010] The temperature of the first hydrothermal reaction is 170-190℃, preferably 180℃.

[0011] The duration of the first hydrothermal reaction is 10-15 hours, preferably 12 hours.

[0012] In step (2), the molar ratio of stannous chloride dihydrate to sulfur source is 1:0.5-2, preferably 1:1.

[0013] The temperature of the second hydrothermal reaction is 150-170℃, preferably 160℃; the time is 10-15 hours, preferably 12 hours.

[0014] Invention Principle: This invention constructs SnS2@SnS heterojunctions on carbon paper substrates via a stepwise hydrothermal method, offering significant advantages over traditional single-phase materials and composite strategies. Tin-based sulfide heterojunctions have become a research hotspot due to their tunable band structure and surface defect engineering advantages. The construction of a SnS2 / SnS heterojunction creates a built-in electric field that promotes charge separation, and the sulfur vacancies at the interface significantly reduce CO2 adsorption energy, providing a new path to overcome performance limits. The core breakthrough of this invention lies in the strong built-in electric field established at the interface between the wide bandgap of SnS2 and the narrow bandgap of SnS. This drives photogenerated electrons to migrate directionally from the SnS2 conduction band to the SnS conduction band, enhancing the CO2 reduction driving force. Simultaneously, holes are reverse-transferred to the SnS2 valence band, suppressing SnS photocorrosion. Crucially, the stepwise temperature gradient hydrothermal method (180℃→160℃) induces a high density of sulfur vacancies at the SnS growth interface, thereby improving CO selectivity by reducing the CO2 adsorption energy and stabilizing the *COOH intermediate. Furthermore, the in-situ growth strategy on a carbon paper substrate replaces the traditional binder system, reducing the interfacial charge transfer resistance. This process uses ethanol as a green solvent, requires no surfactants, and achieves atomic-level interface control of the heterostructure under ambient pressure and low temperature conditions, opening a new pathway for the large-scale preparation of highly efficient photocatalytic CO2 reduction feedstocks.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The photocatalyst prepared by this method has excellent reduction performance, and its reduction yield is as high as 2.15 mmol / cm within 5 hours. -2 Compared with SnS2 alone, its reduction performance is improved by 112.9%; (2) Cost saving: In terms of raw material economy, tin and sulfur are abundant, and the price of commonly used precursors is low, far lower than that of precious metal catalysts; (3) Simple preparation process: It can be synthesized by a simple two-step solvothermal method with a reaction temperature of less than 200℃, without the need for complex equipment, and does not rely on precious metal modification; (4) The process described in this method is environmentally friendly, the preparation process is non-toxic and harmless, and can be loaded onto inexpensive substrates such as stainless steel mesh. Attached Figure Description

[0016] Figure 1Here is a SEM image of the photocatalyst obtained in Example 1; Figure 2 XRD patterns of the photocatalysts obtained from pretreated carbon paper, Example 1, and Comparative Example 1; Figure 3 Figure 1 shows the UV-Vis absorption diagrams of the photocatalysts obtained in Example 1 and Comparative Example 1, where 3a is the UV absorption diagram and Figure 2b is the bandgap diagram calculated from the UV absorption diagram. Figure 4 The bar chart shows the reduction yield test results of the photocatalysts obtained in each experiment. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the embodiments.

[0018] Example 1

[0019] The photocatalyst of the present invention has a flower-shaped layered structure, and its components include SnS2 and SnS, with a molar ratio of SnS2 to SnS of 1-2:1.

[0020] The method for preparing the photocatalyst of the present invention includes the following steps: (1) Take 0.75 mmol tin tetrachloride pentahydrate and 3.75 mmol thioacetamide, add them to 15 ml of alcohol and stir evenly to make a precursor solution. Then add pretreated carbon paper and place it in a reaction vessel. Perform a hydrothermal reaction at 180°C for 12 h to obtain SnS2 material grown on carbon paper.

[0021] The pretreatment process of carbon paper is as follows: the carbon paper is cut into the required size, and then placed in deionized water, acetone and anhydrous ethanol for ultrasonic treatment for 10 minutes. It is then washed with deionized water and dried. The dried carbon paper is then transferred to a plasma machine for carbon fiber plasma surface treatment.

[0022] (2) The SnS2 material was removed and cleaned. Then, 0.375 mmol of stannous chloride dihydrate and 0.375 mmol of thioacetamide were used as precursor solutions for secondary hydrothermal reaction and placed in a reactor. The secondary hydrothermal reaction was carried out at 160°C for 12 h. After cooling, the material was removed, cleaned, and dried to obtain the SnS2@SnS photocatalyst. In this embodiment, the molar ratio of SnS2 to SnS was 2:1.

[0023] Example 2

[0024] The difference from Example 1 is that the amount of stannous chloride dihydrate and thioacetamide added is 0.75 mmol, and the molar ratio of SnS2 to SnS in this example is 1:1.

[0025] Comparative Example 1 The difference from Example 1 is that step (2) is deleted.

[0026] Comparative Example 2 The difference from Example 1 is that the amount of stannous chloride dihydrate and thioacetamide added is 0.25 mmol, and the molar ratio of SnS2 to SnS in this example is 3:1.

[0027] Comparative Example 3 The difference from Example 1 is that the amount of stannous chloride dihydrate and thioacetamide added is 0.1875 mmol, and the molar ratio of SnS2 to SnS in this example is 4:1.

[0028] The photocatalysts obtained in each experiment were tested for CO2 photocatalytic performance using the CEL-PAEM-D8-PLUS photocatalytic activity evaluation system. The results are as follows: Figure 4 .

[0029] Figure 1 The images shown are electron microscope images of the photocatalyst prepared in Example 1 at different magnifications. It can be observed that the SnS2@SnS photocatalyst prepared in this invention has a flower-like shape and a more obvious layered structure.

[0030] analyze Figure 2 All diffraction peaks of the photocatalysts prepared from carbon paper, Comparative Example 1, and Example 1 correspond to standard card JCPDS 23-0677. The bottom layer is pure SnS prepared separately, and all diffraction peaks of pure SnS correspond to standard card JCPDS 00-001-0984. In the figure, all overlapping diffraction peaks (marked by vertical lines) in the XRD pattern correspond from left to right to the (001), (100), (101), and (110) crystal planes of SnS2 and the (011), (012), (102), (110), (013), and (104) crystal planes of SnS. The XRD pattern shows that the prepared sample SnS2@SnS is a heterojunction. The preparation method of SnS is as follows: 0.5 mmol of stannous chloride dihydrate and 0.5 mmol of thioacetamide are added to 15 ml of deionized water and hydrothermally heated at 160°C for 12 hours.

[0031] Depend on Figure 3 It can be seen that the photocatalyst prepared in Example 1 has a narrower bandgap, with a width of 1.83 eV. A narrower bandgap is beneficial for ultraviolet and infrared absorption, thereby improving the reduction performance of carbon dioxide. Figure a shows that the absorbance of the red solid line (Example 1) is higher than that of the black solid line (Comparative Example 1) in most wavelength ranges, especially after the wavelength exceeds 800 nm, where the difference becomes more pronounced. Figure b shows the bandgap widths of the two catalysts calculated from the ultraviolet absorption diagram, confirming that from Comparative Example 1 to Example 1, the bandgap width narrows and the absorbance improves.

[0032] Depend on Figure 4 It can be seen that the photocatalyst prepared by this method has excellent reduction performance, with a reduction yield as high as 2.15 mmol / cm³ within 5 hours. -2 Compared with SnS2 alone, its reduction performance is improved by 112.9%.

Claims

1. A photocatalyst, characterized in that, The photocatalyst has a flower-shaped layered structure, and its components include SnS2 and SnS, wherein the molar ratio of SnS2 to SnS is 1-2.5:

1.

2. A method for preparing the photocatalyst according to claim 1, characterized in that, Includes the following steps: (1) Tin tetrachloride pentahydrate and sulfur source were placed in a liquid and subjected to a first hydrothermal reaction to obtain SnS2; (2) Add stannous chloride dihydrate and sulfur source to SnS2 for a second hydrothermal reaction, then clean and dry to obtain SnS2@SnS photocatalyst.

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of the tin tetrachloride pentahydrate to the sulfur source is 1:3-6.

4. The preparation method according to claim 2, characterized in that, The sulfur source is thioacetamide or thiourea.

5. The preparation method according to claim 2, characterized in that, The liquid mentioned in step (1) is alcohol or deionized water.

6. The preparation method according to claim 2, characterized in that, After the raw materials mentioned in step (1) are mixed, they are added to the pretreated carbon paper. The pretreatment process of the carbon paper is as follows: the carbon paper is cleaned and dried, and then subjected to carbon fiber plasma surface treatment.

7. The preparation method according to claim 2, characterized in that, The temperature of the first hydrothermal reaction is 170-190℃.

8. The preparation method according to claim 2, characterized in that, The duration of the first hydrothermal reaction is 10-15 hours.

9. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of stannous chloride dihydrate to sulfur source is 1:0.5-2.

10. The preparation method according to claim 2, characterized in that, The temperature and time of the second hydrothermal reaction are 150-170℃ and 10-15 hours, respectively.

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